Method of making a light weight orthopedic casting tape

ABSTRACT

The present invention provides an article including a curable resin and a filler associated with the resin. The incorporation of fillers into the casting materials of the present invention adds substantially to the strength of the cured casting material as well as to the handling properties of the uncured casting tape or bandage. The incorporation of fillers into the casting materials of the present invention also imparts air and vapor porosity to the cured casting materials. If desired articles of the present invention may also incorporate fibers (either individually, bundled, or in the form of a light-weight scrim) to provide increased cohesiveness to the uncured article. Extremely moldable casting tapes are also provided which comprise a highly-filled composite material coated on a light-weight scrim. The casting tapes of this embodiment handle like traditional plaster of Paris casts yet cure to a weight-bearing cast in less than one hour.

This is a division of U.S. patent application Ser. No. 08/320,917 filedOct. 11, 1994, which is a continuation-in-part of PCT Patent ApplicationUS94/02950 filed Mar. 17, 1994 which is a continuation-in-part of U.S.patent application Ser. No. 08/184,657 filed Jan. 21, 1994, nowabandoned, which is a continuation-in-part of U.S. patent applicationSer. No. 08/049,007 filed Apr. 16, 1993, now abandoned, which are hereinincorporated by reference.

FIELD OF THE INVENTION

This invention relates to novel curable or thermoplastic compositesuseful in orthopedic casting applications.

BACKGROUND OF THE INVENTION

Many different orthopedic casting materials have been developed for usein the immobilization of broken or otherwise injured body limbs. Some ofthe first casting materials developed for this purpose involved the useof plaster of Paris bandages consisting of a mesh fabric (e.g., cottongauze) with plaster (e.g., calcium sulfate hemihydrate) incorporatedinto the openings and onto the surface of the mesh fabric.

Plaster of Paris casts, however, have a number of attendantdisadvantages, including a low strength-to-weight ratio, resulting in afinished cast which is very heavy and bulky. In addition, plaster ofParis casts develop their strength over a relatively long period oftime, thus making it necessary to avoid weight bearing situations for upto 24 to 48 hours. Furthermore, plaster of Paris casts typicallydisintegrate in water, thus making it necessary to avoid bathing,showering, or other activities involving contact with water.

A significant advancement in the art was achieved when polyisocyanateprepolymers were found to be useful in formulating a resin fororthopedic casting materials, as disclosed, for example, in U.S. Pat.No. 4,502,479 (Garwood et al.), U.S. Pat. No. 4,441,262 (Von Bonin etal.) and U.S. Pat. No. 4,667,661 (Scholz et al). U.S. Pat. No. 4,502,479sets forth an orthopedic casting material comprising a knit fabric whichis made from a high modulus fiber (e.g., fiberglass) impregnated with apolyisocyanate prepolymer resin such as polyurethane. Orthopedic castingmaterials made in accordance with U.S. Pat. Nos. 4,502,479 and 4,667,661provide significant advancement over the plaster of Paris orthopediccasts, including a higher strength-to-weight ratio and greater airpermeability. However, such orthopedic casting materials tend not topermit tactile manipulation or palpation of the fine bone structurebeneath the cast to the extent possible when applying a plaster of Pariscast. In this regard, knit fiberglass materials are not as compressibleas plaster, and tend to mask the fine structure of the bone as the castis applied, e.g., the care provider may be limited in "feeling" the boneduring immobilization of the fracture. Although fiberglass fabrics aresomewhat radiolucent, they sometimes tend to mask the underlying finebone structure to x-ray penetration. Oftentimes a fine mesh or a"shadow" can be seen on the x-ray image. This mesh, corresponding to theknitted fiberglass backing, obstructs the penetration of the x-rays andthereby obscures the fine detail of the underlying bone on the x-rayimage. In addition, knitted fiberglass backings, when cured, are quiterough compared to plaster of Paris casts and often produce casts withsharp edges. The surface roughness and/or sharp edges can cause skinabrasions, snag clothing, and damage household fixtures (e.g., a toiletseat can be easily damaged when a rough fiberglass cast is rubbedagainst it as a person sits down).

Fiberglass backings have further disadvantages. Most, if not all,commercially available fiberglass casting bandages are comprised offilaments with diameters much larger than 3.5 microns (μm). While 3.5 μmfibers are considered by the scientific community to be non-respirable,there exists a sizable number of customers that have become concernedabout the inhalation of fiberglass dust generated during cast removal.Moreover, orthopedic casting materials involving knit fabrics such asfiberglass are somewhat expensive, and may be cost prohibitive for someusers.

An example of an orthopedic bandage using a polyester fabric which isnot a knitted fabric is disclosed in U.S. Pat. No. 3,972,323(Boricheski). However, the orthopedic bandage disclosed in U.S. Pat. No.3,972,323 involves the use of plaster of Paris, and thus is subject tothe disadvantages outlined for plaster of Paris orthopedic casts,including an inferior strength-to-weight ratio and poor airpermeability. A second example of an orthopedic bandage using apolyester fabric which is not a knitted fabric is disclosed in U.S. Pat.No. 4,841,958 (Ersfeld et al.). However, the polyester fabric backingdisclosed in U.S. Pat. No. 4,841,958 causes the cast to have a somewhatlower strength and a lower rigidity than fiberglass casts. Thus, thesecasting materials (when used with an ordinary resin system) require morelayers of casting tape to achieve a weight bearing orthopedic cast.

A cast material comprising a filled thermoplastic crystalline solidpolyurethane is disclosed in U.S. Pat. No. 4,473,671 (Green). In use,the orthopedic cast material is warmed to a sufficiently hightemperature to cause the polymer therein to become soft enough todeform. The orthopedic cast material is molded to conform to the surfaceshape of the effected portion of the body and then is cooled to roomtemperature. The filler of the casting material comprises a blend of 20%to 60% by Weight of calcium metasilicate fibers and from 40% to 80% byweight silica particles. Thermoplastic polymers have also previouslybeen employed in splinting products but have found limited acceptabilitydue to their low porosity. U.S. Pat. No. 4,454,873 (Laufenberg)discloses an orthopedic cast material comprising a thermoplasticmaterial and a coating of (poly)ethylene oxide. The coating is said toprevent adherence of adjacent convolutions of the cast material when itis molten.

A tubular casting system comprising an integral tubular bulky knittedsubstrate carrying a hardenable resin and an undercast padding layer isdisclosed in International Patent Application No. WO 90/14060 (Blott etal.). A water soluble but resin impervious barrier layer intermediate tothe padding and resin bearing layers is discussed.

From the foregoing, it will be appreciated that what is needed in theart is an orthopedic casting material which has both the advantages ofplaster of Paris, e.g., good moldability and palpability of the finebone structure, and the advantages of non-plaster of Paris materials,e.g., good strength-to-weight ratio, fast strength build-up, andpreferably good air permeability. In this regard it would be asignificant advancement in the art to provide such a combination ofadvantages without actually using plaster of Paris, thereby avoiding theinherent disadvantages of plaster of Paris outlined herein. It would bea further advancement in the art to provide such non-plaster of Parisorthopedic casting materials which have as good or better propertiesthan the knitted orthopedic casting materials of the prior art, andwhich can be made to be significantly less expensive, and therefore lesscost prohibitive, than prior art orthopedic casting materials employingknitted fabrics such as fiberglass knits. Such orthopedic castingmaterials and methods for preparing the same are disclosed and claimedherein.

Of related interest are the following U.S. Patent Applications, filed onApr. 16, 1993 by the assignee of this invention: Process and NovelCasting Materials, Ser. No. 08/048,891, now pending; Water Soluble FilmsUsed in Synthetic Casting Tapes, Ser. No. 08/048,738, now U.S. Pat. No.5,603,691; and Novel Casting Tapes and Resins and Processes Therefor,Ser. No. 08/048,656, now U.S. Pat. No. 5,423,785 which are hereinincorporated by reference. Also of related interest are the followingU.S. Patent Applications, filed on Jan. 25, 1993 by the assignee of thisinvention: Water Curable Resin Compositions--Ser. No. 08/008,743, nowU.S. Pat. No. 5,346,939; Orthopedic Support Materials and Method--Ser.No. 08/008,678, now U.S. Pat. No. 5,364,693; and Microfiber Fillers forOrthopedic Casting Tapes--Ser. No. 08/008,755, now U.S. Pat. No.3,354,259 which are herein incorporated by reference.

SUMMARY OF THE INVENTION

In one embodiment, this invention relates to novel curable orthermoplastic composites, useful in orthopedic casting applications,which offer the moldability and conformability of plaster of Paris withthe strength of synthetic fiberglass casting materials. This embodimentprovides a composite article comprising a binder (e.g., a curable resin)and a filler which may be used as a "scrimless" orthopedic casting tape.Preferred materials comprise highly filled resin systems and optionallyincorporate a light-weight mesh fabric for added web integrity. Theincorporation of fillers into the casting materials of this embodimentadds substantially to the strength of the cured casting material as wellas to the handling properties of the uncured casting tape or bandage.The incorporation of fillers into the casting materials of thisembodiment also imparts air and vapor porosity to the cured castingmaterials. Therefore, the disadvantages of fiberglass backings (such aslimited conformability) can be avoided while maintaining the necessaryhigh strength and high rigidity upon cure. If desired, articles of thisembodiment may also incorporate fibers (either as individual randomlyoriented fibers, as fiber bundles, or in the form of a light-weightscrim) to provide increased cohesiveness to the uncured article.

In a presently preferred embodiment, this invention relates to novelcurable casting articles which offer the moldability and conformabilityof plaster of Paris, yet which cure quickly to form a strong article. Inthis embodiment, the casting article is provided in the form of acomposite sheet comprising a mixture of a water curable resin and afiller which is coated on a scrim, preferably a light-weight scrim. Thefiller loading by volume is preferably quite high relative to the volumeof liquid resin, thereby enabling the mixture to be coated even onrelatively light-weight scrims without "pooling". Once activated, thecasting article may be wrapped about a body part and cured. Thisembodiment exhibits exceptionally good moldability and smoothness whileretaining the fast strength build-up of conventional syntheticfiberglass casting materials.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be more clearly understood by reference to thedrawings, wherein:

FIG. 1 shows a schematic representation of a composite structurecomprising spherical particles, resin associated with said particles,and void spaces;

FIG. 2 shows a schematic representation of a composite structurecomprising irregularly shaped particles, resin associated with saidparticles, and void spaces;

FIG. 3 shows a perspective view of a roll form casting tape comprising acomposite casting material and a water-soluble liner film;

FIGS. 3A and 3B show a perspective view of a casting tape comprising acomposite casting material and a water-soluble liner film; and

FIG. 4 shows a perspective view of a roll of casting tape in a watersoluble bag.

FIG. 5 shows a perspective view of a roll form casting tape comprising acomposite casting material sandwiched between two layers of alight-weight scrim material.

FIG. 6 shows a breakaway perspective view of a roll form casting tapecomprising a composite casting material, formed from a plurality ofnarrower strips of casting material, sandwiched between two layers of alight-weight scrim material.

FIG. 7a shows a perspective view of a casting tape comprising a mixtureof a curable resin and filler coated on a light-weight scrim. FIG. 7bshows a cross-section view of the casting tape of FIG. 7a along linesB--B.

FIG. 8 is a scanning electron micrograph of the cross-section of thecasting materials. of Example 31.

In FIG. 1 a portion of a composite article 1 is illustrated, wherein thecomposite article consists of spherical filler particles 2, resindomains 3, and empty void spaces 4. FIG. 2 depicts a similar compositearticle 5, wherein the filler particles 6 are irregularly shaped. FIG. 3shows a partially unwound roll of casting tape 7, comprising a compositecasting material 8, and a fugitive water-soluble liner 9. FIGS. 3A and3B show a perspective view, of a casting tape wherein the castingmaterial 8 is in the form of a sheet which has a fugitive water-solubleliner 9 adjacent to both its major surfaces. FIG. 4 shows a perspectiveview of a roll of casting tape 11 which is enclosed in a water-solublebag 10. FIG. 5 shows a partially unwound roll of casting tape 20,comprising a composite casting material 24, and two layers of alight-weight scrim or web 22. Also shown in FIG. 5 are a plurality ofsurface irregularities 26 which cross the width of the tape andfacilitate transport of water to the center portion of the roll when theroll is immersed in water. FIG. 6 shows a partially unwound roll ofcasting tape 30, comprising a plurality of strips of a composite castingmaterial 34, and two layers of a light-weight scrim or web 32. Alsoshown in FIG. 6 are gaps 38 between the adjacent strips of compositematerial. The gaps facilitate transport of water to the center portionof the roll when the roll is immersed in water. FIGS. 7a and 7b show apresently preferred casting tape 40 of the present invention comprisinga composite mixture 42 of a curable resin and filler coated on alight-weight scrim 44. FIG. 7b shows a cross-section of the tape 40 ofFIG. 7a taken along line B--B. Notably, this cross-section, although notdrawn to scale, illustrates a tape 40 having a relatively thick coatingof composite mixture (comprising resin 46 and filler 48) on a relativelythin, light-weight scrim 44. The coating is able to be easily moldedduring application and thereby conform to the desired shape.

DETAILED DESCRIPTION OF THE INVENTION

In one embodiment, the present invention relates to porous orthopediccasting materials and methods for preparing and using such orthopediccasting materials, wherein the materials comprise a binder (e.g., acurable resin) which is associated with a filler. In particular, theresins and fillers employed in the present invention have importantcharacteristics and physical properties which allow the materials topossess sufficient strength for use as an orthopedic casting materialeven without the use of a separate scrim. The materials also have thenecessary porosity and radiolucency for use as an orthopedic castingmaterial and possess improved tactile manipulability, moldability, andpalpability. At the same time, the orthopedic casting materials of thisembodiment are relatively inexpensive, thus providing a more economicalalternative to the orthopedic casting materials presently known in theart which often employ knitted fiberglass fabrics.

The porous materials of this embodiment may be supplied in tape, splint,tubular and various laminate forms. The porous materials of thisembodiment are, in general, characterized as high filler contentmaterials which are held together by a "binder" component (i.e., eithera curable resin or a thermoplastic polymer). Preferably the fillerloading is high enough and the binder content low enough that thecomposite product is porous to air and moisture. While not intending tobe bound by theory, it is presently believed that the binder serves tobond the particles together at point locations as depicted in FIGS. 1and 2. Voids between the particles are presently believed to provideporosity to the cured composite. As used herein, a cast which hassufficient porosity to allow moisture vapors produced by the skin tofreely escape through the cured cast is said to be "breathable" or to"breathe."

In another embodiment, the present invention relates to orthopediccasting tapes comprising a composite mixture of a curable resin and afiller coated on a preferably light-weight scrim. When uncured, theresin and filler composite mixture has important characteristics andphysical properties (e.g., rheological properties) which allow themixture to possess sufficient integrity for use as a coating on alight-weight scrim. Casting tapes of this embodiment exhibit exceptionalsmoothness during application and handle in a manner similar to plasterof Paris. When cured, the materials also have the necessary strength foruse as an orthopedic casting material and during curing possess improvedtactile manipulability, moldability, smoothability and palpability.

Conformability of current synthetic casting materials is often limitedby the fabric backing (i.e., "scrim") used to carry the composite. Sincethe presently preferred casting materials of the present invention haveonly a very light fabric backing or no fabric backing the conformabilityis limited primarily by the rheology of the composite (i.e., resin andfiller mixture). Combination of suitable fillers and resins of thepresent invention will provide a product having exceptional moldability.Casting materials which exceed the moldability of traditionalPlaster-of-Paris materials have been obtained. The finished cast orsplint of the present invention is also preferably strong, light-weight,radiolucent, and porous.

Suitable fillers for use in the present invention comprise inorganic ororganic, particulate or fibrous materials which are insoluble in thecurable resin. Filler morphologies may include spheres, bubbles,expandable bubbles, particulate materials, filaments, microfibers,flakes and platelet type materials, as well as combinations of these.The fillers may have a solid, porous, or hollow structure. Preferredfillers are light-weight and of a shape which does not pack particularlywell thereby preferably ensuring sufficient void volume to render thecomposite sufficiently porous to moisture vapor. More preferably, thefillers have a generally spherical shape and the composite is porous tomoisture vapors. Most preferably, the casting products of the presentinvention are as porous as traditional fiberglass knit casting tapes.

Suitable inorganic filler materials include: glass, amorphous andcrystalline silica (SiO₂), soda lime borosilicate, amorphoussodium/potassium/aluminum silicate glass, alumina (aluminum oxide), ironoxides, calcium metasilicate, calcium carbonate, calcium sulfate (ineither a particulate or microfiber form), kaolin, mica, talc, bariumsulfate, boron fibers, carbon fibers, glass fibers, ground glass fibers,flake glass, metallic fibers, feldspar, barium ferrite, titanium oxide,ceramics and the like. Preferred inorganic filler materials includeglass and ceramic bubbles such as: Scotchlite™ brand glass bubblesH50/10000 EPX, H50/10000 (acid washed), K-46, and S60/10000 (availablefrom 3M); Extendosphere™ brand SG, CG, SF-12 (available from PQ Corp.);Zeeosphere™ brand 200, 400, 600, 800, and 850 (available from 3M);Zeolite™ W1000, W1012, W1300, W1600, G3400, and G3500 (available from3M); Dicaperl™ brand HP-900 and HP-920 (available from Grefco) andSil-Cell™ brand Sil-35/34, Sil-32, Sil-42, and Sil-43 (available fromSilbrico Corp., Hodgkins, Ill. 60525). Dicaperl™ brand HP-820, HP-720,HP-520, HP-220, HP-120, HP-900, HP-920, CS-10-400, CS-10-200, CS-10-125,CSM-10-300, and CSM-10-150 (available from Grefco, Torrance, Calif.),and ceramic particles such as Ceramcel™ (in sizes from 1.5 mm to 5 mmand available from Microcel Tech. Inc.) may also be suitable,particularly when blended with other fillers. Colored pigment fillersare also suitable. Blends of these fillers may also be suitable.

Suitable organic fillers include fillers comprised of thermoplastic orthermoset organic materials or both as well as composite fillermaterials comprising the afore-mentioned organic materials as matrix andinorganic micro-inclusions dispersed therein. Suitable organic fillersare insoluble in the curable resin. Suitable thermoplastic fillermaterials include polyolefins such as Primax brand UH-1080, UH-1060 andUH-1250 (available from Air Products & Chemicals--Allentown, Pa.),polyesters (e.g., poly(ethylene terephthalate), hereinafter referred toas "PET"), polyamides, polyimides, polyacrylates, polycarbonate,polyurethane and the like including copolymers of the aforementionedmaterials. Suitable thermoplastic filler materials also includeexpandable bubbles such as Expancel 461 DE 20 microspheres (availablefrom Nobel Industries). Suitable thermoset filler materials includeepoxies, aldehyde condensation products (e.g., Ucar Thermosetmicroballoons BJO-0950, BJO-0820, BJO-0900, BJO-0840, BJO-09300available from Union Carbide, Danbury Conn.), acrylates, andmethacrylates. Preferred organic filler materials include polyethylenemicrospheres (available from Air Products & Chemicals--Allentown, Pa.).

Preferred particulate fillers have an average particle diameter between5 and 500 μm, more preferably the particulate fillers have an averageparticle diameter between 20 and 200 μm, most preferably the particulatefillers have an average particle diameter between 30 and 120 μm. A usedherein, "average particle diameter" is defined as the diameter of asphere of the same volume as the particle.

Microfibers may be added to the resin to enhance web integrity orcomposite strength. Preferred fibers for use in the present inventionhave an average length between 25 and 5,000 μm, more preferably thefibers have an average length between 30 and 1,000 μm, most preferablythe fibers have an average length between 30 and 500 μm. Microfiberfillers such as those described in U.S. patent application Ser. No.08/008,751, which is herein incorporated by reference, may also beuseful alone or in combination with other particulate fillers or fibers.

Preferred fillers for use with isocyanate functional polyurethaneprepolymers systems include: Scotchlite™ brand glass bubbles H50/10000EPX, H50/10000 (acid washed), and S60/10000; Sil-Cell™ brand Sil-35/34,Sil-32, Sil-42, and Sil-43; Primax™ UH-1080, UH-1060 and UH-1250; andDicaperl HP-820, HP-720, HP-520, HP-220, HP-120, HP900, HP920,CS-10-400, CS-10-200, CS-10-125, CSM-10-300, and CSM-10-150. Beneficialresults have been demonstrated using a combination of spherical fillersand a fiber such as 1.5 denier×19.05 mm long PET fibers (available fromMinifibers--Code No. 6 1575).

Suitable concentrations of filler in the resin (i.e., "filler loading")will vary depending on the bulk density of the filler, the specificgravity of the filler and particular resin employed, and the desiredporosity and handling property of the composite. As used herein,"specific gravity" refers to the ratio of the density of a substance tothe density of a reference substance. For solids and liquids thereference substance is water (density=1 g/cc), therefore the specificgravity of a solid or liquid is numerically equal to its density. Thespecific gravity of the filler particles is preferably less than 3, morepreferably less than about 2 and most preferably less than 1. A suitablefiller loading is determined by selecting a level which is sufficientlyhigh to ensure adequate strength (and preferably good porosity) but notso high that the composite easily fractures or crumbles or is otherwisedifficult to apply.

One method of characterizing the porosity of a composite is to measurethe volume fraction of void space in the composite material (hereinafterreferred to as the composite's "void volume"). The void volume of acomposite material is the unoccupied space of the composite which isaccessible to the transport of air or water vapor. The void volume of acomposite material may be measured as described in Example 14. Forexample, spaces which are filled with a gas (e.g., air or CO₂) and whichare accessible to the transport of air or water vapor would be includedin the void volume of the composite. The void volume may be convenientlyexpressed as a percentage of the composite's total volume. Forcomposites which include components that are themselves porous (e.g.,the composite comprises a porous filler), the void volume of the porouscomponent should be included in the total void volume of the compositeprovided the component's voids are accessible to the transport of air orwater vapor. For samples which exhibit resin foaming during cure (suchas an isocyanate functional resin system) the void volume should becalculated by measuring the volume uptake of an inert solvent of lowsurface tension as described in Example 14. An inert solvent, as used inthis test, is a solvent which does not appreciably swell or dissolve thecured composite. Isopropyl alcohol is a suitable inert solvent for mostisocyanate functional resins systems. It is believed that resin foamingmay create closed cell voids which are not accessible to the transportof air or water vapor and would not be included by the test described inExample 14. Notably, resin foaming may create open cell voids at thesurface of the composite and closed cell voids throughout the material.Care should be taken when measuring void volume to ensure that the voidsare accessible to the transport of air or water from either surface ofthe composite (i.e., that the solvent penetrates the whole thickness).

An important characteristic of preferred casting materials is a highstrength to weight ratio. In order to ensure a light weight composite,preferred fillers have a bulk density of less than 1.0 g/cm³, morepreferred fillers have a bulk density of less than 0.75 g/cm³ and mostpreferred fillers have a bulk density of less than about 0.6 g/cm³. Afiller's "bulk" density or "apparent" density, as used herein, isdetermined by weighing the amount of filler which occupies a unitvolume. To make this determination a 10 gm sample of filler is placedinto a suitable sized graduated cylinder (e.g., about 25 cm³) so thatthe filler occupies about half its height. The cylinder is then gentlyshaken side-to-side for 5 minutes to allow settling. The volume offiller is then read from the graduations on the cylinder side.

The articles of the present invention may also be provided as a tape orsheet form having a plurality of macroscopic holes through itsthickness. A "macroscopic hole," as used herein, is a hole which extendsthrough the thickness of the tape. In contrast, the previously mentioned"void volume" or "pores" are characterized as void spaces surroundingindividual particles of the composite material. The void spaces aredispersed throughout the composite but, while providing a path throughwhich water vapor may escape, do not form foraminous "holes" through thethickness of the tape. As a further guide to differentiating a "pore"from a "hole" it is presently believed that a pore has a diameter lessthan 1000 μm, while a hole has a diameter of 1000 μm or more.

The articles of the present invention may also be provided as a tape orsheet form having a plurality of macroscopic surface irregularities(e.g., out-of-plane bumps or depressions) which run transverse acrossthe tape or sheet and extend to or near the edge of the sheet and limittight contact of adjacent layers of a roll. These surface irregularitiesfacilitate migration of water to the center portion of a roll of tape,e.g., when curing is being initiated. Preferably, these surfaceirregularities are easily smoothed out when the initiated tape is moldedinto a cast.

Preferred porous composites of the present invention contain between 30and 85 percent by volume filler, more preferably, between 40 and 75percent by volume filler, and most preferably, between 50 and 70 percentby volume filler. Preferred porous composites of the present inventionhave between 8 and 40 volume percent resin, more preferably, between 10and 30 volume percent resin, and most preferably, between 12 and 25volume percent resin. Preferred porous composites of the presentinvention have at least 7 percent void volume, more preferably, at least10 percent void volume, and most preferably, at, least 12 percent voidvolume.

Preferred orthopedic casting tapes which comprise a composite mixture ofa curable resin and a filler coated on a light-weight scrim containbetween 30 and 85 percent by volume filler, more preferably, between 40and 75 percent by volume filler, and most preferably, between 50 and 70percent by volume filler. Preferred orthopedic casting tapes whichcomprise a composite mixture of a curable resin and a filler coated on alight-weight scrim have between 8 and 40 volume percent resin, morepreferably, between 10 and 30 volume percent resin, and most preferably,between 12 and 25 volume percent resin. It is desirable that therheology of the composite mixture be adjusted so that the compositemixture can be easily coated on the light weight scrim at the desiredcoating weight, yet does not "pool" during storage. Surprisingly, it hasbeen discovered that such a mixture can be achieved by thoroughly mixinga filler into a resin system, wherein the resin system comprises a blendof prepolymer materials. The composite mixture (comprising filler, andresin components) is then coated onto the light-weight scrim before theresin system has developed its final molecular weight (and hence itsviscosity has not built up fully). After the composite mixture has beencoated on the scrim, the resin builds up additional viscosity due to areaction between the prepolymer components. Thus, the composite mixtureachieves a final storage rheology which resists pooling. It has beendiscovered that the volume ratio of filler to resin provides animportant indication of a composite material's likely rheologicalproperties. As the volume fraction of filler to resin is increased thecomposite is likely to become increasingly viscous and, consequently,less likely to pool. Preferred composite mixtures for coating onlight-weight scrims have a volume ratio of filler to resin (V_(f)/V_(r)) of at least 0.4, more preferably at least 0.6, and mostpreferably at least 0.8.

Preferred fillers for use with water curable resins also have very lowmoisture absorbency. Preferably the filler contains less than 4% byweight absorbed water, more preferably the filler contains less than 1%by weight absorbed water and most preferably the filler contains lessthan 0.5% by weight absorbed water. The amount of absorbed water in afiller sample may be determined by heating the filler in an oven andmeasuring the sample's weight loss. For fillers that have a high amountof moisture one may preferably dry the filler prior to incorporationinto the composite.

The shelf stability of the composite mixture is an importantconsideration when selecting suitable filler and resin combinations.Shelf stability refers to the ability of the finished product to resistdegradation or significant increase in viscosity during normal storageconditions. For example, for products comprising isocyanate functionalpolyurethane prepolymers such standard storage conditions would includestorage in a moisture free environment at 25° C. Notably, manycommercially available fillers, such as glass bubbles, are basic innature (i.e., alkali) and may cause undesirable side-reactions inisocyanate functional polyurethane prepolymers. These side reactions maycause the resin to harden prematurely or prevent hardening at all.Preferred fillers are chosen so as to not upset the shelf stability ofthe resin material. The shelf stability of a casting material preferablyexceeds 1 year when stored at ambient temperature (i.e., 25° C.), morepreferably the shelf stability of a casting material exceeds 3 yearswhen stored at ambient temperature and most preferably the shelfstability of a casting material exceeds 5 years when stored at ambienttemperature. The shelf stability of a casting material may also betested at elevated temperature (49° C.) to predict ambient temperaturestability. Preferred casting materials withstand four weeks at 49° C.,more preferred casting materials withstand eight weeks at 49° C., andmost preferred casting materials withstand twelve weeks at 49° C. Whenisocyanate functional polyurethane prepolymers systems are employed itis beneficial to ensure that the fillers are neither basic in nature norcontain basic impurities. Such basicity can result in side reactions(such as trimerization, allophonate formation, and biuret formation)with the isocyanate functional resin system which may limit the shelfstability of the product. Adverse effects of the basicity of the fillermay be minimized by washing and/or neutralizing the filler with asuitable acid or by addition of an acid stabilizer to the resin.

If desired, the fillers may be surface treated using silanes, titanates,zirconates and the like to enhance resin bonding, ease of mixing, andcompatibility. The surface treatment may be performed prior toincorporation of the filler into the resin or in-situ, i.e., the surfacetreatment agent may be incorporated into the resin for later reactionwith the filler.

As previously mentioned, a curable resin may be employed as a binder.The curable-resin used in the casting material of the invention ispreferably any curable resin which will satisfy the functionalrequirements of an orthopedic cast. Obviously, the resin must benontoxic in the sense that it does not give off significant amounts oftoxic vapors during curing which may be harmful to either the patient orthe person applying the cast and also that it does not cause skinirritation either by chemical irritation or the generation of excessiveheat during cure. Furthermore, the resin must be sufficiently reactivewith the curing agent to insure rapid hardening of the cast once it isapplied but not so reactive that it does not allow sufficient workingtime to apply and shape the cast. Initially, the casting material mustbe pliable and formable and should adhere to itself. Then in a shorttime following completion of cast application, it should become rigidor, at least, semi-rigid, and strong to support loads and stresses towhich the cast is subjected by the activities of the wearer. Thus, thecasting material must undergo a change of state from a viscoelasticcondition (e.g., a moldable putty) to a solid condition in a matter ofminutes.

In one embodiment, the resins are highly viscoelastic water-curableresins which resists "pooling", even when coated on a very light-weightscrim. In another embodiment, the resin, when mixed with the filler,forms a highly viscous mixture which resists "pooling", even when coatedon a very light-weight scrim. As taught herein, many traditionalnon-viscoelastic resins may be modified to be highly viscoelastie (i.e.,the resin's tan δ value is decreased) and therefore suitable for use inthis invention. Presently preferred are urethane resins formed by thereaction of a polyisocyanate and a polyol such as those disclosed inU.S. Pat. No. 4,131,114. A number of classes of water-curable resinsknown in the art are suitable, including polyurethanes, cyanoacrylateesters, and, when combined with moisture sensitive catalysts, epoxyresins and prepolymers terminated at their ends with trialkoxy- ortrihalo-silane groups. For example, U.S. Pat. No. 3,932,526 disclosesthat 1,1-bis(perfluoromethylsulfonyl)-2-aryl ethylenes cause epoxyresins containing traces of moisture to become polymerized.

Resin systems other that those which are water-curable may be used,although the use of water to activate the hardening of an orthopediccasting tape is most convenient, safe and familiar to orthopedicsurgeons and medical casting personnel. Preferred resins are notappreciably dispersible in water. Resins such as those disclosed in U.S.Pat. No. 3,908,644 in which a bandage is impregnated with difunctionalacrylates or methacrylates, such as the bis-methacrylate ester derivedfrom the condensation of glycidyl methacrylate and bisphenol A(4,4'-isopropylidenediphanol) are suitable. The resin is hardened uponwetting with solutions of a tertiary amine and an organic peroxide.Also, the water may contain a catalyst or initiator. For example, U.S.Pat. No. 3,630,194 proposes an orthopedic tape impregnated withacrylamide monomers whose polymerization is initiated by dipping thebandage in an aqueous solution of oxidizing and reducing agents (knownin the art as a redox initiator system). The strength, rigidity and rateof hardening of such a bandage are subject to formulation variables asdisclosed herein. The following disclosure relates primarily to thepresently preferred embodiments of the invention wherein water-curableisocyanate-functional prepolymers or water reactive liquidorganometallic compounds are employed as the curable resin.

Some presently more preferred resins for use in the present inventionare water-curable, isocyanate-functional prepolymers. Suitable systemsof this type are disclosed, for example, in U.S. Pat. Nos. 4,411,262,and 4,502,479. Presently more preferred resin systems are disclosed inU.S. Pat. No. 4,667,6151 and U.S. patent application Ser. No.07/376,421, now U.S. Pat. No. 5,570,822, which is herein incorporated byreference. A water-curable isocyanate-functional prepolymer as usedherein means a prepolymer derived from a polyisocyanate compound and areactive hydrogen compound or oligomer (e.g., a "polyol"). As usedherein, a reactive hydrogen compound is a compound having activehydrogen in accordance with the well known Zerevitinov test asdescribed, for example, in Chemistry of Organic Compounds by Carl R.Noller, Chapter 6, pp. 121-122 (1957). The prepolymer has sufficientisocyanate-functionality to cure upon exposure to water, e.g., moisturevapor, or preferably liquid water.

It is presently preferred to employ a polyisocyanate prepolymer formedby the reaction of an isocyanate and a polyol. It is preferred to use anisocyanate which has low volatility such as diphenylmethane diisocyanate(MDI) rather than a more volatile material such as toluene diisocyanate(TDI). Suitable isocyanates include 2,4-toluene diisocyanate,2,6-toluene diisocyanate, mixture of these isomers, 4,4'-diphenylmethanediisocyanate, 2,4'-diphenylmethane diisocyanate, mixture of theseisomers together with possible small quantities of 2,2'-diphenylmethanediisocyanate (typical of commercially available diphenylmethanediisocyanate), and aromatic polyisocyanates and their mixture such asare derived from phosgenation of the condensation product of aniline andformaldehyde. Typical polyols for use in the prepolymer system includepolyalkylene oxides (e.g., polyethylene oxide and polybutylene oxide),polypropylene ether glycols (available from Arco Chemical under thetrade name Arcol™ PPG and from BASF Wyandotte under the trade namePluracol™), polytetramethylene ether glycols (Polymeg™ from the QuakerOats Co. or Terathane™ from the Du Pont de Nemours, E. I., Co.,Wilmington Del.), polycaprolactone diols Tone™ series of polyols fromUnion Carbide), and polyester polyols (hydroxyl terminated polyestersobtained from esterification of dicarboxylic acids and diois such as theRucoflex™ polyols available from Ruco division, Hooker Chemical Co.). Byusing high molecular weight polyols, the rigidity of the cured resin canbe reduced.

An example of a resin useful in the casting material of the inventionuses an isocyanate known as Isonate™ 2143L available from the DowChemical Company (a mixture of di- and tri-isocyanates containing about73% of MDI) and a polypropylene oxide polyol from Union Carbide known asNiax™ PPG725. To prolong the shelf life of the material, it is preferredto include from 0.01 to 1.0 percent by weight of benzoyl chloride oranother suitable stabilizer (based on total resin weight).

The reactivity of the resin once it is exposed to the water curing agentcan be controlled by the use of a suitable amount of proper catalyst.The reactivity must not be so great that: (1) a hard film quickly formson the resin surface preventing further penetration of the water intothe bulk of the resin; or (2) the cast becomes rigid before theapplication and shaping is complete. Good results have been achievedusing 4- 2- 1-methyl-2-(4-morpholinyl)ethoxy!ethyl!-morpholine ("MEMPE")prepared as described in U.S. Pat. No. 4,705,840 and 2,2'dimorphiolinodiethyl ether ("DMDEE") prepared as described in U.S. Pat.No. 4,433,680, the disclosure of which are incorporated by reference, ata concentration of about 0.05 to about 5 percent by weight (based ontotal resin weight).

Foaming of the resin should be minimized since it may adversely impactthe surface smoothness of the cast and may decrease the cast's overallstrength. Foaming may occur, for example, when carbon dioxide isreleased as a result of water reacting with an isocyanate group. One wayto minimize foaming is to reduce the concentration of isocyanate groupsin the prepolymer. However, to have reactivity, workability, andultimate strength, an adequate concentration of isocyanate groups isnecessary. Although foaming is less at low resin contents, adequateresin content is required for desirable cast characteristics such asstrength and resistance to peeling. A satisfactory method of minimizingfoaming is to add a foam suppressor such as silicone Antifoam A (DowCorning), or Anti-foam 1400 silicone fluid (Dow Corning) to the resin.It is especially preferred to use a silicone liquid such as Dow CorningAnti-foam 1400 at a concentration of about 0.05 to 1.0 percent byweight. Water-curable resins containing a stable dispersion ofhydrophobic polymeric particles, such as disclosed in U.S. patentapplication Ser. No. 07/376,421, now U.S. Pat. No. 5,570,822, and laidopen as European Published Patent Application EPO 0 407 056, may also beused to reduce foaming.

In addition lubricants may be added to the resins in accordance withU.S. Pat. No. 4,667,661 such that the casting materials exhibit reducedtack prior to and during cure and yet form a cast with acceptablestrength and lamination strength. Suitable lubricants include:hydrophilic groups which are covalently bond to the resin system;additives which are incompatible with the curable resin including: asurfactant, a polymer comprised of a plurality of hydrophilic groups,and a polysiloxane; and combinations of the above. The lubricant may beused in conjunction with a separate fugitive liner if desired.

Also included as presently preferred resins in the instant invention arenon-isocyanate resins such as water reactive liquid organometalliccompounds. These resins are preferred as an alternative to isocyanateresin systems. Water-curable resin compositions suitable for use in anorthopedic cast consist of a water-reactive liquid organometalliccompound and an organic polymer. The organometallic compound serves toreduce resin viscosity and is a compound of the formula (R¹ O)_(X)MR².sub.(y-x) wherein: each R¹ is independently a C₁ -C₁₀₀ hydrocarbongroup, optionally interrupted in the backbone by 1-50 nonperoxide --O--,--S--, --C(O)--, or --N-- groups; each R² is independently selected fromthe group consisting of hydrogen and a C₁ -C₁₀₀ hydrocarbon group,optionally interrupted in the backbone by 1-50 nonperoxide --O--, --S--,--C(O)--, or --N-- groups; x is an integer between 1 and y, inclusive; yis the valence of M; and M is boron, aluminum, silicon, or titanium. Theorganic polymer is either an addition polymer or a condensation polymer.Addition polymers are preferably utilized as the organic polymerconstituent. Particularly useful addition polymers are those made fromethylenically unsaturated monomers. Commercially available monomers,from which such addition polymers can be formed, include but are notlimited to, ethylene, isobutylene, 1-hexene, chlorotrifluoroethylene,vinylidene chloride, butadiene, isoprene, styrene, vinyl napthalene,ethyl acrylate, 2-ethylhexyl acrylate, tetrahydrofurfuryl acrylate,benzyl acrylate, poly(ethylene oxide)monoacrylate, heptafluorobutylacrylate, acrylic acid, methyl methacrylate, 2-dimethylaminoethylmethacrylate, 3-methacryloxypropyltris(trimethylsiloxy)silane, isobutylmethacrylate, itaconic acid, vinyl acetate, vinyl, stearate,N,N-dimethylacrylamide, tert-butyl acrylamide, acrylonitrile, isobutylvinyl ether, vinyl pyrrolidinone, vinyl azlactone, glycidylmethacrylate, 2-isocyanatoethyl methacrylate, maleic anhydride, vinyltriethoxysilane, vinyl tris(2-methoxyethoxy)silane, and3-(trimethoxysilyl)propyl methacrylate. Polymers bearing hydrolyzablefunctionality are preferred. An acidic or basic catalyst may be used toaccelerate the water cure of these compositions. Strong acid catalystsare preferred. A more complete description of suitable water reactiveliquid organometallic compounds is disclosed in pending U.S. patentapplication Ser. No. 08/008,678, now U.S. Pat. No. 5,364,693 and Ser.No. 08/008,743, now U.S. Pat. No. 5,346,939, which are hereinincorporated by reference.

Also included as presently more preferred resins in the instantinvention are the water curable alkoxy silane terminated oligomersdisclosed in copending U.S. Patent Application "Novel Casting Tapes andResins and Processes Therefor," Ser. No. 08/048,656, now U.S. Pat. No.5,423,735. These resin compositions are preferably solventless.

Preferred resin compositions are stable, i.e., nonreactive, and do notsignificantly increase in viscosity at a temperature of less than about40° C. In addition, preferred resin compositions are capable of curingupon exposure to water to form a hardened material at a temperaturebetween about 10° to 100° C., preferably at a temperature between about20° to 50° C. Preferred resin compositions include a low viscositywater-reactive alkoxysilane terminated polymer. The average alkoxysilanefunctionality is at least one and preferably at least two but may be ashigh as four. Each alkoxysilane group may have 2 or 3 hydrolyzablegroups.

The water-reactive polymer having hydrolyzable terminal alkoxysilanegroups is preferably a compound of the formula: ##STR1## wherein: Q is apolyol residue;

W is --NHC(O)--X(R² _(2-n-q))-- or --XC(O)NH--;

X=--O--, --NR⁸ --, or --S--;

Y is --O--, --NR⁸ --, --S--, carbamylthio (--SC(O)NH--), carbamate(--OC(O)NH), or ureido, and N-substituted ureido (--NHC(O)NH--);

R¹ is a substituted or unsubstituted divalent bridging C₁ -C₁₀₀hydrocarbon group, optionally interrupted in the backbone by 1 to 50nonperoxide --O--, --C(O)--, --S--, --SO₂ --, --NR⁶ --, amide(--C(O)--NH--), ureido (--NH--C(O)--NH--), carbamate (--O--C(O)NH--),carbamylthio (--S--C(O)--NH--), unsubstituted or N-substitutedallophanate (--NH--C(O)--N(C(O)--O--)--), unsubstituted andN-substituted biuret (--NH--C(O)--N(C(O)--N--)--), and N-substitutedisocyanurate groups;

R² can be present (if n=1) or absent (if n=2) and is selected from thegroup consisting of a H and a substituted or unsubstituted C₁ -C₂₀hydrocarbon group, optionally interrupted in the backbone by 1 to 10nonperoxide --O--, --C(O)--, --S--, --SO₂ --, or --N(R⁶)-groups;

R³ is a substituted or unsubstituted divalent bridging C₁ -C₂₀hydrocarbon group, optionally interrupted in the backbone by 1 to 5nonperoxide --O--, --C(O)--, --S--, --SO₂ --, or --N(R⁶)-- groups;

R⁴ is a C₁ to C₆ hydrocarbon group or --N═C(R⁷)₂ ;

each R⁵ and R⁷ is independently a C₁ to C₆ hydrocarbon group;

R⁶ is a C₁ to C₆ hydrocarbon group, or hydrogen;

R⁸ is selected from the group consisting of a H and a substituted orunsubstituted C₁ -C₂₀ hydrocarbon group, optionally interrupted in thebackbone by 1 to 10 nonperoxide --O--, --C(O)--, --S--, --SO₂ --, or--N(R⁶)-- groups;

n=1 to 2 and q=0 to 1, with the proviso that when X is N, n+q=1, andwhen X is S or O, n+q=2;

u=the functionality of the polyol residue=0 to 6, with the proviso thatwhen u=0, the compound of Formula I is ##STR2## m=2 to 3; and z=1 to 3.

Each "R³ --Si(OR⁴)_(m) " moiety can be the same or different. Apreferred composition consists of toluene diisocyanate ("TDI") basedpre-polymers end-capped with highly functionalized alkoxy silanes, suchas bis(trimethoxysilylpropyl)amine.

For use in preparing alkoxy silane functionalized prepolymers, thecurrently preferred prepolymers precursors are those formed from polyolsand reactive polyisocyanates with free NCO ranging from 1.9 to 9.0percent and contain polyethylene glycol, polypropylene glycol,polytetramethylene glycol, polyester ether polyols and mixtures ofthese. The most preferred diisocyanate prepolymers are those containingpolyethylene glycol, but include polyether polyols such aspolytetramethylene glycol, polypropylene glycols, polybutylene glycols,and random or block copolymers of these, and polymer polyols such asthose disclosed in U.S. patent application Ser. No. 07/376,421, now U.S.Pat. No. 5,570,822. Polyolefin polyols such as polybutadiene polyols andpolyisoprene polyols may also be used as well as aromatic and aliphaticamine terminated "polyols" such as Jeffamine and Polamine materials, lowmolecular weight diols, thiols and the like. Mixtures and blends ofthese polyols may be useful. The preferred average polyol functionalityis 1.8 to 3, more preferably 2 to 2.5 but polyols with functionalitiesas high as 4 or more may be useful.

For use in preparing alkoxy silane terminated prepolymers, the preferredpolyisocyanates have differential reactivity, i.e. have at least oneisocyanate group which is significantly more reactive than one or moreisocyanate groups on the same molecule by a factor of 2 or more. Thepreferred isocyanates have a functionality of 2 to 3 while particularlypreferred materials have functionalities of 2 to 2.3. The presentlypreferred isocyanate is TDI. Other aromatic isocyanates such asmethylene diisocyanate ("MDI") and polyisocyanates based on condensationproducts of formaldehyde and aniline are potentially useful. Aliphaticisocyanates are useful and may be particularly preferred forapplications where stability to ultraviolet light is of particularconcern. Materials such as the trimer and biuret adducts ofhexamethylene isocyanate ("HMDI"),methylene-bis-(4-cyclohexylisocyanate), tetramethylxylene isocyanate("TMXDI"), and xylene isocyanate could be used. Materials such asisophorone diisocyanate and the like are perhaps useful due to thedifferential reactivity of the isocyanate groups.

For use in preparing alkoxy silane terminated prepolymers, the preferredreactive silane of the present invention isbis(trimethoxysilylpropyl)amine, but other reactive silanes could beemployed such as aminopropyltrimethoxysilane ("A-1110"),N-beta-(aminoethyl)-gamma-aminopropyl-trimethoxysilane ("A-1120"),gamma-mercaptopropyltrimethoxysilane ("Y-11167"), isocyanatopropyltrimethoxysilane, etc. Note that critical elements for a silane usefulin the present invention are that it have: at least one active hydrogengroup (except when W=--XC(O)NH--); at least one silane functionality;and at least 2 (and preferably 3) hydrolyzable groups in the silane(s).

Preferred silanes are trimethoxy- and triethoxy silanes but othertrialkoxy, alkyldialkoxy, aryldialkoxy, and oximino silanes could beuseful. These could also be reacted in various combinations andproportions with the TDI-based prepolymers to produce a wide range ofaverage silane functionality (e.g., 2 to 4 or more).

Another important ingredient in the alkoxysilane terminated prepolymerresins is the catalyst for the moisture curable resin. It has been foundthat substituted guanidines and particularlyN,N,N',N'-tetramethylguanidine ("TMG") is the preferred catalyst forthese silane cure systems ensuring a sufficiently rapid hydrolysis ofthe alkoxysilane groups and subsequent condensation of the resultingsilanols to form siloxane adducts. However, other basic tertiary aminecatalysts could be used in this resin system such as 1,8-diazobicyclo5,4,0!undecan-7-one ("DBU"), triethylamine, imidazoles, piperazines,etc. Acid catalysts such as sulfonic acids (including alkyl andperfluoroalkyl), carboxylic acids (including alkyl and perfluoroalkyl),phosphoric acids, boric acids and the like could also be employed withthis resin system. Moreover, various metal catalysts such as ligands oftin, cobalt, bismuth, lead, zinc or titanium which are known to the artof silane cure could be used alone or in combination with theafore-mentioned catalysts in this resin system.

In one embodiment, the present invention provides porous compositematerials with enhanced cohesiveness prior to hardening, most preferablywithout using a heavy fabric backing. Where a fabric backing may bedeemed desirable, preferably only a light backing is used. Preferably,the resin system is highly cohesive to ensure the composite materialwill not crack as the product is molded and will support typical tensileforces which are placed on the uncured composite during the applicationprocedure. When formulating the porous composite materials of thepresent invention one must strike a balance between the material'suncured "handling" properties (such as web cohesiveness, moldability,smoothability, resistance to pooling, etc.) and the material's curedphysical properties (such as strength, porosity, surface smoothness,etc.). It is presently believed that the material's physical propertiesare substantially affected by the composite's filler to resin ratio.Unfortunately, as the filler to resin volume ratio is increased (therebyincreasing cured composite porosity) the composite may become lesscohesive or smoothable and more difficult to mold. For a given fillerand resin system it may not be possible to formulate a composite whichhas both high strength and porosity and has good cohesiveness and/orsmoothability in the uncured state. To alleviate this problem twodifferent approaches are disclosed in the present invention. The firstapproach involves, a modification to the resin component of thecomposite. This modification causes a decrease in the resin's tan δ andthereby increases the composite's cohesiveness. The second approachinvolves the incorporation of fibers into the composite (either asindividual fibers or as a fabric scrim). The fibers provide enhancedcohesiveness to the composite and support some of the tensile forceswhich are placed on the uncured composite during application. Acombination of these methods may be employed if desired.

In another embodiment, a casting tape is provided comprising a highlyviscous mixture of resin and filler coated on a light-weight scrim. Thecoating on the casting tape, when activated, is highly movable so thatthe tape can be molded to form a smooth, plaster-like cast. Whenformulating the coated casting tapes of this embodiment one must strikea balance between the material's uncured "handling" properties (such asmoldability, smoothability, resistance to pooling, etc.) and thematerial's cured physical properties (such as strength, surfacesmoothness, etc.). It is presently believed that the material's physicalproperties are substantially affected by the composite's filler to resinvolume ratio. Unfortunately, as the filler to resin ratio is increased(thereby increasing the coating's viscosity and resistance to pooling)the composite may become less smoothable and more difficult to mold. Incontrast, if the filler to resin ratio is too low, the coating may poolfrom the scrim backing or may not be able to be coated at a sufficientlyhigh coating thickness or weight and thus not provide a cast havingsufficient strength or rigidity.

A porous composite's handling properties may be characterized bymeasuring the resin component's viscoelasticity using a suitablerheometer. A suitable rheometer for evaluating the preferred materialsof the present invention include cone and plate or parallel platerheometers such as the Rheometrics Dynamic Analyzer-II ("RDA-II"),available from Rheometrics Inc. When operated in a dynamic shear modethe rheometer is capable of measuring the elastic- or storage-modulus(G'), viscous- or loss-modulus (G"), and dynamic viscosity (η_(o)) ofthe material. The ratio of G" to G' is referred to as tan delta (tan δ)and is a good measure of the material's overall viscoelastic behavior.In general, tan δ is greater than 1 for a liquid and less than 1 for asolid. When operated in a steady shear mode a parallel plate rheometeris capable of measuring the viscosity (η) as a function of the appliedshear rate (γ).

As previously mentioned, dramatically decreasing the tan δ of the resincomponent is one method of enhancing the porous composite's (i.e., theresin and filler mixture's) cohesiveness and may be accomplished in avariety of ways. These include: (1) incorporating (i.e., solubilizing) asuitable amount of a high molecular weight secondary polymer into thecurable resin; (2) forming an interpenetrating polymer network with thecurable resin, e.g., by forming a secondary polymer in-situ through useof a co-cure polymer system; or (3) providing a high concentration ofurethane, urea, or other hydrogen bonding functionalities to promotechain interaction; or (4) incorporating prepolymers with a relativelyhigh level of chain branching thereby promoting chain entanglement.Combinations of the above methods may also be employed.

Suitable high molecular weight secondary polymers are those polymerswhich are sufficiently soluble, dispersible or swellable in the curableresin and are capable of decreasing the resin's tan δ. Suitablesecondary polymers may actually bring the resin to a gel state.Particularly preferred polymers are those polymers which are capable ofhydrogen bonding or otherwise interacting with the curable resin systemin order to provide adequate viscoelasticity at relatively low additionlevels. In general, the amount of secondary polymer added to the resinshould provide a suitable tan δ value to the resin (and therefore thenecessary cohesiveness to the composite) yet not adversely impact thestrength and integrity of the cured system. The amount of secondarypolymer required to accomplish this function will often depend on themolecular weight of the polymer and the viscosity of the unmodifiedcurable resin or composite. In general, polymer properties (includingrheological properties) are much more dependent on the larger sizedmolecules in a sample than on the smaller ones. Therefore, theweight-average molecular weight value of a polydisperse sample is a muchbetter indicator of the properties to be expected in a polymer blendthan the number average molecular weight and will be used herein unlessotherwise noted. When cohesiveness is achieved by incorporation of ahigh molecular weight polymer, preferred mixtures of polymer and curableresin comprise up to 30% polymer, more preferably between 1 and 20%polymer and most preferably between 2 and 12% polymer. Presentlypreferred high molecular weight secondary polymers for use in the resinsystems of the present invention have a weight average molecular weight("M_(w) ") between about 30,000 and 5,000,000. More preferably, the highmolecular weight secondary polymers have a weight average molecularweight between 100,000 and 3,000,000. Most preferably, the highmolecular weight secondary polymers have a weight average molecularweight between 250,000 and 2,000,000.

A preferred polymer is a polymer which is capable of significantlydecreasing the tan δ of the resin when added to the resin atconcentrations less than about 20% and preferably less than about 10% byweight such that tan δ of the resin and polymer mixture is less than 20at 1.0 rad/sec, more preferably less than 10 at 1.0 rad/sec, and mostpreferably less than 5 at 1.0 rad/sec. In addition, a preferred polymeris a polymer which is capable of significantly increasing the storagemodulus of the resin when added to the resin at concentrations less thanabout 20% and preferably less than about 10% by weight such that G' isat least 0.1 dyne/sq cm at 0.1 rad/sec and 1 dyne/cm at 1 rad/sec.Preferably the polymer is capable of increasing G' to values over 1dyne/cm and 10 dyne/cm at frequencies of 0.1 and 1.0 rad/secrespectively.

Polyvinylpyrrolidone ("PVP") and copolymers of N-vinylpyrrolidone havebeen found to be particularly useful polymers for decreasing the tan δof polyurethane prepolymer systems. PVP is generally soluble in manypolyethylene glycols and polytetramethylene glycols and may be directlyadded as solids and vacuum dried in-situ while heating between about100° C. and 150° C. Alternatively, resins systems comprising PVP andpolyol may be dried azeotropically using an appropriate solvent followedby solvent removal. Once dissolved in the polyol the resin and polymersolution is preferably formulated under process conditions which preventthe separation of the PVP from the solution. It has also been observedthat undried PVP is a particularly useful polymer for decreasing the tanδ of polyurethane prepolymer systems. It is presently believed that themoisture added to the resin system (i.e., when using undried PVP havingup to about 5 wt. % water) causes chain extension of the prepolymer witha resulting increase in hydrogen bonding of the urea groups so formed.Presently preferred polyurethane prepolymer resin systems comprisebetween 1 and 8% polyvinylpyrrolidone in the resin (based on the totalresin weight and exclusive of any filler). Presently more preferredresin systems comprise between 2 and 6% by weight PVP in the resin.Presently preferred polyvinylpyrrolidone for use in the presentlypreferred resin systems of the present invention has a weight averagemolecular weight between about 30,000 and 3,000,000. More preferably,the PVP has a weight average molecular weight between 100,000 and2,000,000. Most preferably, the PVP has a weight average molecularweight between 250,000 and 1,500,000.

Other suitable polymers for use in the preferred polyurethane prepolymerresin system include acrylate copolymers such as copolymers of isooctylacrylate and N-vinylpyrrolidone ("NVP"), copolymers of C1-C14 acrylatesand methacrylates (such as butyl acrylate, butyl methacrylate, isooctylacrylate, isooctyl methacrylate, acrylic acid, methacrylic acid andcopolymers of butyl acrylate and hydroxyethyl methacrylate),acrylamides, and methacrylamides. Other suitable polymers are thosepolymers formed from monomers such as N-vinyl pyrrolidone, vinyl acetateand its hydrolyzed polymeric derivatives, styrene, olefins,acrylonitrile and the like. It should be pointed out that such suitablemonomers can also be ionic or may contain substituent groups (such asamino, mercapto, hydroxy, and carboxyl groups) which are reactive withthe primary polymer system. High molecular weight polyalkylene oxides(preferably having a molecular weight greater than 20,000, morepreferably having a molecular weight greater than 100,000) such aspolyethylene oxide, polypropylene oxide, and polybutylene oxide as wellas block and random copolymers of these may also be useful as thesecondary polymer system. Preferred polymers and copolymers includethose based on butyl acrylate, butyl methacrylate, isooctyl acrylate,isooctyl methacrylate, acrylic acid, hydroxyethyl methacrylate,acrylamide, N-vinylpyrrolidone, and polyethylene oxide. It is understoodthat these polymers may be polymerized in-situ within the primary resinsystem or a component of the primary resin, polymerized in a solvent andadded to the finished primary resin system, polymerized in a componentof the primary resin system such as the polyol or isocyanate, or addedto a component of the primary resin system such as the polyol orisocyanate.

An alternative method of providing a highly viscoelastic resin (therebyfacilitating the formation of a cohesive composite) is by forming aninterpenetrating polymer network with the curable resin, e.g., byforming a secondary polymer in-situ through use of a co-cure polymersystem. One method of accomplishing this goal is by incorporating asecond reactive monomer or oligomer system, which is independentlyreactive, into the primary curable resin. Suitable second reactivemonomers or oligomers are preferably independently reactive from theprimary curable resin and are capable of forming, in-situ, a highmolecular weight secondary polymer. This method offers the potentialadvantage of allowing processing of the composite material into itsfinal form, or close to its final form, while it still has a relativelylow viscosity. The second reactive monomer or oligomer may then bepolymerized to form a secondary polymer thereby increasing theviscoelasticity of the resin blend. For example, an unsaturated secondmonomer or oligomer (such as a mono- or poly-functional acrylate,methacrylate, acrylamide, or methacrylamide) may be added to anisocyanate functional prepolymer resin system. The second monomer oroligomer may then be polymerized through the use of, for example, heatand/or actinic radiation (visible or ultraviolet light, electron-beam,etc.) to form a polymer therein. This polymerization step may beperformed during the manufacturing process or by the user. Morepreferably the second reactive monomer or oligomer may also containfunctional groups which will allow the second polymer to react with theprimary cure system. For example, acrylate or methacrylate alcohols(such as hydroxyethylmethacrylate "HEMA") are capable of reacting via afree radical mechanism to form a linear polymeric polyol. This polymeris capable of reacting with an isocyanate resin system. Alternatively,an epoxy homopolymerization may be performed through the use of suitablecatalysts yielding a polymer containing hydroxyl groups which arecapable of further reacting with the isocyanate functional resin. Insystems where the second reactive monomer or oligomer also containsfunctional groups which will allow the formed second polymer to reactwith the primary cure system, the ratio of NCO groups to OH groupspreferably should be controlled so that sufficient residual reactiveisocyanate functionality remains thereby ensuring a rapid and completecure during application of the device. In addition, the extent ofcrosslinking of the second reactive monomer or oligomer should becontrolled in order to avoid excessive brittleness of the curedcomposite which may lead to cast breakage by a patient.

A further alternative method of providing a highly viscoelastic resin(thereby facilitating the formation of a cohesive composite) is byproviding a composition having a high concentration of urethane, urea,or other hydrogen bonding functionality. Suitable additives comprisegroups which are capable of promoting hydrogen bonding or polymer chaininteraction within the uncured resin system or both. Alternatively, theresin may comprise components with high amounts of chain branching orhigher molecular weight oligomers which promote chain entanglements. Ifdesired, both methods may be employed in combination. In the previouslydiscussed isocyanate functional polyurethane prepolymer systems, theincorporation of higher levels of hydrogen bonding functionality may beaccomplished by increasing the number of urethane groups per unit weightof resin and/or incorporating urea groups formed by the reaction ofprimary or secondary amine functional materials with the isocyanategroups of the resin. The number of urethane groups per unit weight ofresin may also be increased through the addition of water to the resin(with a commensurate loss of carbon dioxide). In general, the relativenumber of urethane groups in the resin will increase as the ratio ofisocyanate equivalents to alcohol equivalents (NCO/OH ratio) of aparticular resin system is decreased. Furthermore, the relative numberof urethane groups in the resin can be increased by using polyols oflower equivalent weights (higher OH numbers). Additional chainentanglement may also be provided by incorporation of higher molecularweight polyol components and/or by increasing chain branching throughthe incorporation of polyols and/or isocyanates having a functionalitygreater than 2. The average functionality can be as high as 6 but ispreferably less than 4 and is typically between 2 and 3. Wheremodification to the functionality of the resin is the primary means ofincreasing the viscoelasticity of the resin the functionality ispreferably between 2.5 and 3.5. A sufficient amount of hard segment(e.g. isocyanate) should be provided to ensure adequate stiffness forrigid immobilization applications. For systems based on Isonate 2143Lthe concentration of Isonate should be preferably greater than 45% byweight and more preferably greater that 50% by weight and mostpreferably greater than 54% by weight of the resin component (withoutfiller) to ensure the final composite is sufficiently stiff.

As previously mentioned, the process of applying (e.g., wrapping) a castto a patient's limb imparts a tensile force or stress to the castingbandage or tape. Similarly, the application of a splint to a patient'slimb also stresses the splint material. Suitable casting or splintmaterials should readily accommodate these application stresses and notbreak apart during the cast application procedure. Preferred castingtapes of the present invention have a tensile strength greater thanabout 0.0175 N/mm width, more preferred casting tapes have a tensilestrength greater than about 0.0875 N/mm width, and most preferredcasting tapes have a tensile strength greater than about 0.175 N/mmwidth.

Traditional casting products distribute these stresses on a heavy-weightfabric backing or scrim (e.g., a fiberglass knit). In contrast, thepresent invention provides casting materials which in some cases havesufficient cohesiveness to resist these application stresses evenwithout a heavy weight fabric backing or scrim (e.g., by decreasing theresin component's tan δ through the incorporation of a high molecularweight secondary polymer into the resin, etc.). However, a secondalternative approach to increase the cohesiveness of the materials ofthe present invention, i.e. to impart higher tensile strength prior tocuring and/or increased resistance to cracking during application andcuring, is the incorporation of macrofibers into the composite (eitheras individual fibers or as a fabric scrim). In this approach,macrofibers provide enhanced cohesiveness to the composite and supportsome of the tensile forces which are placed on the uncured compositeduring application. This is particularly preferred for ease ofprocessing the material. Most preferably, a light scrim may be utilizedto perform this function. A combination of these approaches is alsopossible.

Suitable macrofibers for increasing the cohesiveness of the uncuredcomposite include both inorganic fibers and organic fibers. Sintableinorganic fibers include: fiberglass, and ceramic fibers. Suitableorganic fibers include fibers made from: polyester, polyamide (includingnylon and Kevlar), polyolefin, polyacrylate, rayon, cotton, hemp, jute,natural rubber, and polyurethane materials. Blends of fibers may also beuseful. Suitable fibers have average lengths at least 0.5 cm. Preferredfibers have average lengths between 0.5 and 8 cm, more preferably thefibers are between 1 and 5 cm in length. The fibers may be multifilamentor monofilament materials and may comprise filaments between 0.5 and 300denier. It has been found that incorporation of as little as 1 to 2% byweight of polyester fibers results in a significant improvement in webintegrity and cohesiveness. It is presently believed that incorporationof from 1 to 30% by weight of a suitable fiber may be beneficial.

As previously mentioned, it may be beneficial to incorporate a lightconformable scrim into the material. This approach is presentlypreferred when fabricating orthopedic casting tapes which are highlysmoothable and moldable. One such presently preferred tape is describedin further detail in Example 24. The scrim may be on the surface of thecomposite but is preferably embedded or partially embedded in thematerial. Preferred scrims are light-weight and generally comprise lessthan 30%, more preferably less than 20% by weight of the composition.The light-weight nature of these preferred scrims does not permitcomplete absorption of the binder into the fiber bundles. Consequently,a significant amount of composite mixture (e.g., resin and filler) liesatop the scrim and is "available" for molding and conforming. Theavailable composite mixture can in some instances move relative to thelight-weight scrim and form a very smooth cast surface. Notably,preferred composite mixtures for use with preferred light-weight scrimshave sufficient viscosity or yield stress to resist undesirable"pooling" during normal use and storage. Preferred composite mixtureshave a viscosity of at least 100 Pa s, more preferably at least 400 Pas, most preferably at least 1,000 Pas when tested at 1 rad/s.

The scrims are preferably porous to allow the composite coated scrim topass moisture, vapor, and air. Preferred scrims are thin with fairlylarge openings in order to allow bonding of the material on either sideof the embedded scrim. Suitable scrims include knits, wovens, non-wovensand extruded porous sheets (e.g. materials from Conweb, Minneapolis,Minn.). Cheese cloth has proven to be quite useful. Preferred scrimshave a basis weight between 5 and 30 grams/m², more preferably between 8and 26 grams/m², most preferably between 8 and 17 grams/m². Alight-weight scrim (6 grams/m²) comprising 1.75 denier, 3.8 cm longpolyester staple fibers and coated at a basis weight of 2 grams/m² withRoplex B15 resin (available from Rohm & Hass Co., Philadelphia, Pa.19105) is particularly suitable. Another suitable light-weight and lowcost scrim is a spunbonded nonwoven made from polymers includingpolypropylene, polyester, polyethylene, and polyamide. Because of itslow cost and drapability polypropylene is the preferred polymer. Asuitable spunbonded polypropylene nonwoven with good openness to allowsufficient water penetration through a roll of coated nonwoven duringwater activation and sufficient conformability when wrapping thematerial is RFX™ nonwoven fabric (available from AMOCO Fabrics andFibers Company, Atlanta, Ga.) in a basis weight of 16.7 g/m². Other websmay be substituted if desired.

If desired, a heavier scrim such as a traditional fiberglass knit may beutilized in the casting products of the present invention. While this isnot preferred, for the reasons previously mentioned, fiberglass knitsprovide sufficient support and porosity. Suitable scrims for use in thepresent invention are disclosed in pending U.S. patent application Ser.No. 08/008,751, now U.S. Pat. No. 5,405,643, which is hereinincorporated by reference. Where fiberglass backings are desired,suitable sheets which may be employed are knit fiberglass fabrics suchas disclosed in U.S. Pat. Nos. 4,502,479; 4,609,578; 4,668,563; and5,014,403 and in U.S. patent application Ser. No. 07/976,402, now U.S.Pat. No. 5,353,486. Particularly preferred sheets of this type areextensible, heat-set fabrics as disclosed in U.S. Pat. No. 4,609,578(Reed) which is herein incorporated by reference. When heavier-weightscrims are employed, suitably heavier coating weights may also beemployed to maintain a smoothable feel to the sheet. Preferably, thecoating weight of composite mixture (e.g., resin and filler) is greaterthan the weight which is absorbed by the fiber bundles of the sheet.This ensures that a portion of the composite mixture is available at thesurface of the sheet to provide the preferred smoothable feel.

In practice the scrim may be incorporated between two thin sheets ofhighly filled resin composition. Alternatively, more than one scrim maybe utilized to form a laminate sheet with the highly filled resincomposition. For example, two scrims may be used to "sandwich" a sheetof highly filled resin composition. This can be accomplished by pressingthe scrims against the surfaces of a sheet of highly filled resincomposition, e.g., through a nip roller. In addition, the scrim may bepre-coated with a resin which facilitates bonding of the adjacent layersof highly filled resin composition. The pre-coated resin may be similarto the resin in the composite or may comprise a different composition,such as a pressure sensitive adhesive.

A preferred process for making a casting tape comprising a coating of ahighly filled composite mixture (comprising curable resin and filler) ona light-weight scrim involves coating the composite mixture on the scrimwhile the composite mixture viscosity is relatively low. In onepresently preferred method the composite mixture is coated on thelight-weight scrim while the curable resin is only partially reacted(i.e., the curable resin at the time of coating comprises a mixture ofprepolymers). Thus, the coating has a low enough viscosity to spread outon the scrim. Additional filler may then be dusted on the surfaces ofthe coated scrim if desired. This process is further described inExample 24. In another method the composite mixture may be diluted witha volatile solvent which lowers the viscosity of the mixture and whichis readily removed after being coated on the scrim.

The present invention also provides casting materials containing resinswhich possess a smoothable feel during application. It has been foundthat the initial water absorbency of a resin system can be controlled bythe proper selection of polyol and isocyanate and, if present, thesecondary polymer. For example, these components can be blended toprovide a resin which is sufficiently hydrophilic to allow the resin tobecome smoothable and feel "movable" or actually allow movement of theresin much like plaster of Paris. This facilitates a smooth finish tothe cast and greatly enhances cast moldability.

Incorporation of suitable amounts of a hydrophilic polyol such aspolyethylene glycol into the resin formulation provides a smoothableresin upon water activation. Yet even when the resin becomes movable nomess is created if the filler level of the composite is maintained highenough and/or the resin is sufficiently viscoelastic. Nevertheless, asthe resin becomes even more movable it may be necessary for theclinician to wear gloves to avoid transfer to the hands. Preferredcomposite systems incorporate a sufficient amount of hydrophiliccomponents to provide a movable resin. For systems that comprise apolyisocyanate prepolymer resin, creamy movable composites can beprepared by increasing the curable resin's NCO/OH ratio which generallyresults in more free isocyanate and in a decreased resin viscosity.Suitable smoothable resins have an NCO/OH ratio greater than 2.0.Preferred smoothable resins have an NCO/OH ratio greater than 2.5, morepreferably greater than 3.0, most preferably between 3.0 and 3.9. Asused herein "movable" or "movable resin" refers to a resin which afteractivation with water but before setting becomes smoothable on thesurface and can be physically redistributed by hand to smooth thesurface of the molded cast in a manner similar to a plaster of Pariscast although perhaps not to the extent possible with plaster of Paris.As a result, the moldable materials of the present invention do notappreciably stick to the gloves of the applier, nor drip significantamounts of material onto the floor causing a mess.

Smoothability of the composite is important because it allows the use ofinexpensive fabrics which may not conform perfectly to the shape of thebody part simply by wrapping the material on. The smoothability of thecomposite allows any tucks and folds to be blended into the cast. Inaddition, smoothability allows the practitioner to make a smooth castwhich is non-abrasive to the patient's skin and clothing. Furthermore,smoothability greatly increases the ease of molding the cast for thedesired fit and clinical requirements for proper healing. Smoothabilityin the present invention is defined as the ability to sufficientlysmooth the curable or hardenable portion of the casting tape or splintby hand rubbing to produce an even surface. Preferably, the texture ofthe scrim, and any overlap areas resulting from wrapping and folding ofthe tape become blended into the surface so as to make these features nolonger readily apparent.

To achieve the smoothability of the present invention, the compositemust have a sufficiently low viscosity when water activated. This can becontrolled by adjusting the resin composition and filler content asdescribed previously. For example, higher NCO:OH ratios and lower fillerlevels reduce the viscosity. When measured according to Example 30, theviscosity of the water activated material is preferably less than2.5×10⁴ Pa s, more preferably less than 1.8×10⁴ Pa s, and mostpreferably less than 1.2×10⁴ Pa s. In addition, the composite preferablycontains a slip agent or lubricant to prevent the composite fromsticking to the gloves of the applier and thus allow easy movement ofthe hands over the surface of the cast being formed. Suitable lubricantsare described in U.S. Pat. No. 4,667,661. Furthermore, the compositemust be available in sufficient quantity on the surface of the scrim toallow for the desired smoothability. Traditional synthetic castingmaterials contain the resin within the fiber bundles of the fabric,thereby making the resin unavailable for smoothing the surface of thecast made therefrom. To make sufficient composite available forsmoothing purposes it is desired that at least a 50 micron thickness ofcomposite be available on the exposed surfaces of the fibers comprisingthe scrim upon which the composite is coated. More preferably, at leasta 100 micron thickness of composite is available, and most preferably a150 to 300 micron thickness of composite is available.

Resin systems may also be colored for decorative purposes using dyes orpigments or both. Luminescent pigments may also be employed.Furthermore, one may alternatively wrap the splint or cast of thepresent invention with a decorative or informative sheet comprisingraised lettering and/or figures which is capable of leaving impressionsin the material. Furthermore, the materials of the present invention maybe printed using suitable dyes or pigments by direct or indirectprinting methods such as transfer printing, pigment printing, or ink jetprinting.

The materials and compositions of the present invention may befabricated into a variety of configurations including splints, tapes,and preformed shapes such as tubes. When fabricated as a splint, thematerial may be provided as a precut slab or a continuous length formwith or without a covering and/or padding. Suitable coverings andpaddings for use in this invention are discussed in U.S. Pat. Nos.5,027,803 and 4,899,738 which are herein incorporated by reference. Thesplint may have a padding material on one or both sides. The materialsand compositions of the present invention may also be supplied as aprepadded unitary splint in tubular form such as that illustrated inFIG. 6 of U.S. Pat. No. 5,027,803.

A fugitive water soluble web may be employed as a liner which separatesadjacent layers of the tape (e.g., when the tape is provided as a roll)and which may enhance the tape's cohesiveness. When used with a watercurable resin the liner is preferably dried prior to being placed incontact with the resin. Preferably, the liner is rapidly soluble inwater and effectively dissolves when exposed to water in less than about60 seconds (as defined in the examples below), more preferably the linerdissolves when exposed to water in less than 30 seconds and mostpreferably the liner dissolves when exposed to water in less than 10seconds. Preferred liners also provide a lubricating effect to the tapewhen dissolved. By "effectively dissolve" is meant that the liner whenmixed with water under the desired conditions of use will solubilize inthe water to an extent sufficient to provide a lubricating effect orallow layer-to-layer adhesion of the casting material or both. Morepreferably the liner when mixed with water under the desired conditionsof use dissolves to form a homogeneous liquid mixture. Suitable watersoluble liners are comprised of polymers such as polyvinylalcohol("PVA") and copolymers of PVA (as used herein, the term polyvinylalcoholrefers to copolymers derived from, for example, the hydrolysis ofpolyvinyl acetate, wherein the extent of hydrolysis is preferablygreater than 50 percent, more preferably greater than 80 percent),polyacrylamides, polymers incorporating acrylic acid, cellulose etherpolymers such as hydroxypropylmethylcellulose, hydroxypropyl cellulose,and hydroxyethylcellulose, polyethyloxazoline, polyethylene oxide (asused herein "polyethylene oxide" and "polyethylene glycol" aresynonymous terms), polyethylene oxide and polypropylene oxide random andblock-copolymers, esters and urethanes of polyethylene glycol orpolyethylene glycol and polypropylene glycol polymers and the like.Copolymer films and laminates and polymer blends are also possible.

Preferably the liner has sufficient flexibility for processing. Someliner materials (e.g., certain PVAs) may require the incorporation of aplasticizer to achieve a suitable degree of flexibility for use as aliner. Suitable plasticizers may be incorporated into the liner either"internally" or "externally" to the polymer component. An example of aplasticizer which is "internally" incorporated into the liner is apolymer formed by copolymerizing vinyl acetate with polyethylene glycolmonomethacrylate (the plasticizer) followed by hydrolysis to PVA andextrusion as a film. An example of a plasticizer which is "externally"incorporated into the liner is the blending of glycols or other smallmolecules such as esters into a polymer melt. The plasticizer preferablyis extremely dry for use with the presently preferred water curableresins. However, for thermoplastic casting materials a low concentrationof water may serve as the plasticizer. Suitable liner films includecontinuous or non-continuous films. Suitable non-continuous filmsinclude woven or non-woven films such as melt blown PVA films. Being ina non-continuous form such as a non-woven fabric may facilitatedissolution of the liner due to the greatly exposed surface area.Furthermore, porous structures may also provide greater flexibilitywhich may facilitate processing. In use the liner begins dissolving assoon as the product is contacted with water and therefore need not beremoved or even perceptible to the clinician. Liners are preferably keptthin to prevent excessive build up of polymer solution which couldinterfere with layer to layer lamination of the casting tape. Continuousfilm liners are preferably less than 100 μm thick, more preferably lessthan 60 μm thick, and most preferably less than 25 μm thick. While theliner itself provides lubrication, an additional lubricant such asdisclosed in U.S. Pat. No. 4,667,661 may be added to the composition.

The presently most preferred liner for use with water-curable castingtapes is Aicello Solublon PVA film SA grade 17 micron thick availablefrom Mitsui Plastics Inc. (White Plains, N.Y.). Although, even when dry,this film is potentially reactive with isocyanate functionalwater-curable resins (since it contains "hydroxyl" functionality) it hasbeen observed that this reaction does not readily occur. It is presentlybelieved that undesirable reactions between such liners and resins canbe prevented provided the liner and resin are maintained in a separate"phase" (i.e., the liner should preferably be essentially insoluble inthe resin).

For purposes of retarding resin migration (e.g., on systems where theresin is susceptible to "pooling") the liner is preferably a continuousfilm and is wound up along with the casting tape such that through thecross section of the roll the layers of casting tape and lineralternate. Alternatively, the liner may be placed on both sides of thecasting tape during the winding operation. Furthermore, the liner, ifplaced on both sides of the casting tape, may be sealed on one or bothedges to further prevent resin pooling and migration. In the absence ofsuch a seal, and in order to gain the full benefit of this embodiment,the roll of casting tape is preferably stored laying on its side ratherthan on an end. If stored on an end, with an unsealed edge downward, theresin could possibly still pool. However, since many casting tapes arecurrently boxed and stored on their sides this may not be a problem.

In another embodiment of the present invention a thermoplastic polymeris employed as a binder (i.e., a casting tape or splint is provided as a"thermoplastic" composite). This embodiment offers an environmentallyfriendly and hazard-free alternative in casting. Casting materials ofthis embodiment do not require cumbersome disposable liners and willprovide a moldable slippery material which is easy to apply. Inaddition, the product will have very good conformability and should beinexpensive to manufacture.

The basic elements of the thermoplastic composite of the presentinvention include: a thermoplastic polymer with controlled amorphousphase rheology, the thermoplastic polymer preferably being softened atless than about 75° C.; an optional water soluble liner; and asubstantial proportion of inert fillers as previously described. Thethermoplastic casting tapes of the present invention may also comprisecomponents containing one or more reactive functional groups suitablefor cross-linking the article.

Suitable thermoplastic polymers for use in the present invention arethose polymers which soften or melt at temperatures which cancomfortably be withstood by the patient and/or technician during thecast's application. This temperature is believed to be less than about90° C., preferably less than about 75° C., although somewhat highertemperatures may be acceptable (especially in situations where directcontact of the casting material and skin are avoided). Suitablethermoplastic polymers include polyurethanes (especially polyurethanesbased on semi-crystalline polyester polyols), polyethylene, ethylenevinyl acetate, cis and trans polyisoprene, polyesters such aspolycaprolactone and the like. The currently preferred thermoplasticpolymers for use in the present invention are semi-crystallinepolyesters. Polycaprolactone and blends of polycaprolactone areparticularly preferred.

In this embodiment the thermoplastic polymer is substituted for thecurable resin and provides a similar function (i.e., holding the fillertogether). Thermoplastic casting materials are applied to the patientafter first heating the material above its softening temperature (e.g.,in the case of semi-crystalline materials above their melt temperature).Heating of the material may be accomplished in a variety of waysincluding immersion in hot water, contact with steam, exposure tomicrowave radiation, contact with dry heat, etc. The use of water orsteam is particularly preferred in product constructions whichincorporate a water soluble liner and/or hydrophilic resin lubricant.Microwave heating is suitable for materials which absorb microwaveenergy or employ a microwave susceptor. The warmed casting material isthen molded to the desired shape and cooled to harden.

The following examples are offered to aid in understanding of thepresent invention and are not to be construed as limiting the scopethereof. Unless otherwise indicated, all parts and percentages are byweight.

EXAMPLES Example 1 Casting Article Comprising Resin and Glass Bubbles

To a beaker containing 13.3 g of glass bubbles (having a specificgravity of 0.60 and available as "SSX" from 3M Company, St. Paul, Minn.)was added 26.6 g of a resin consisting of components shown in thefollowing table:

                  TABLE 1                                                         ______________________________________                                        Component             Parts                                                   ______________________________________                                        Isonate 2143L (Dow Chemical Co.)                                                                    54.83                                                   MEMPE.sup.1           1.75                                                    Benzoyl chloride      0.07                                                    DB-100 Silicone Fluid.sup.2                                                                         0.18                                                    IONOL.sup.3           0.49                                                    Arcol PPG 725 (Arco)  42.68                                                   ______________________________________                                         .sup.1 "MEMPE" = 4 2 1methyl-2-(4-morpholinyl)ethoxy!ethyl!morpholine.        .sup.2 Now known as Dow Corning Antifoam 1400.                                .sup.3 "IONOL" = 2,6di(tertiarybutyl)-4-methylphenol or "BHT".           

In a dry environment (i.e., less than 4% relative humidity) the mixturewas stirred with a spatula, then kneaded. An additional portion (3 g) ofglass bubbles was added and kneaded in to provide a dry to the touchputty-like composite which was 38% by weight filler and had a ratio offiller volume to resin volume (V_(f) /V_(r)) of 1.06.

Curing of the composite was initiated by placing it under running tapwater having a temperature of approximately 25° C. The moist compositewas molded around two fingers and cured in 2 to 4 minutes. The compositewas easy to mold and very conformable during curing. It was smooth andsnow white. After curing for 24 hours it was strong enough to permit aperson weighing 63.5 kg to stand upon the composite on the fingerswithout damaging the composite.

Example 2 Casting Article Comprising Resin, Glass Bubbles andCheesecloth

A 300 g portion of poly(N-vinyl)pyrrolidone (having a weight averagemolecular weight of 360,000 and available from Aldrich Chemical Company,Milwaukee, Wis.) was added to a 5 liter flask containing 2700 g ofCarbowax 600 polyol preheated to 49° C. (available from Union Carbide,Danbury, Conn.). The aforementioned polymer is hereinafter referred toas "PVP-360." A vacuum (0.5 torr) was drawn upon the closed flask andthe mixture was slowly heated to 120° C. and maintained at thattemperature for a total of 2 hours until water evaporation stopped inorder to dry the mixture. The solution obtained was cooled to about 49°C. and stored in a 49° C. oven.

Resin was formulated by mixing the ingredients shown in the followingtable in the order shown. The mixture was warmed and shaken vigorouslyby hand for 5 to 10 minutes after the addition of the Carbowax600/PVP-360 solution until a homogeneous solution resulted. After allcomponents were added the mixture was placed on a shaker for 0.75 hour,then allowed to stand for about 16 hours at 25° C.

                  TABLE 2                                                         ______________________________________                                        Component           Parts                                                     ______________________________________                                        Isonate 2143L       384.82                                                    Carbowax 600/PVP solution                                                                         215.30                                                    Benzoyl Chloride     0.35                                                     DB-100               1.26                                                     Ionol                3.36                                                     MEMPE                10.50                                                    Carbowax 1450 polyol                                                                              112.39                                                    ______________________________________                                    

In a first batch, to 40 g of Scotchlite™ H50/10,000 EPX glass bubbles(having a specific gravity of 0.5 and available from 3M Company) whichhad been dried by heating at 140° C. for about 16 hours was added 26.7 gof the resin from Table 2. The mixture was kneaded by hand until it washomogeneous, then rolled fiat into a 9.53×30.5×0.635 cm teflon moldlined with PVA film (Aicello Solublon SA grade, Mitsui Plastics Inc.,White Plains, N.Y.) using a teflon coated metal rolling pin. Thecomposite was removed from the mold and the PVA film was peeled off. Theresulting composite (V_(f) /V_(r) =3.1) was placed fiat and stored in aconventional cast pouch of polyethylene coated aluminum foil.

In a second batch, to 40 g of Scotchlite™ H50/10,000 EPX glass bubbleswhich had been dried by heating at 140° C. for about 16 hours was added26.7 g of the resin from Table 2 resulting in composite having V_(f)/V_(r) =3.1. The batch was separated into two approximately equalportions, one of which was formed into a composite layer 3.18 mm thickin the previously described teflon mold. A layer of conventionalcommercially available cheese cloth which had been impregnated with asmall amount of the resin of Example 1 was placed over the compositelayer and the second half of the batch which had also been formed into a3.18 mm layer in the same teflon mold was sandwiched over the cheesecloth. The laminate was rolled with the teflon coated metal roller pinto ensure the layers were well bonded and stored in apolyethylene-coated aluminum foil pouch.

A third casting article was prepared by adding 28.5 g of Dicaperl HP 900glass bubbles (having a specific gravity of 0.33 and available fromGrefco Inc., Torrence, Calif.) to 27 g of the resin of Table 2 andkneading until the mixture (having a V_(f) /V_(r) =3.32) washomogeneous, then separating the batch into two equal portions, forminga laminate of 3.18 mm thickness as described above around untreatedcheesecloth and rolling the laminate with a roller pin. While thelaminate did not separate, it is believed that they would separate moreeasily than the laminate described as the second batch. It was stored ina standard polyethylene-coated aluminum foil pouch.

Each of the laminated casting articles of the present Example wasremoved from the storage pouches and immersed in warm water to initiatecuring. Casts were formed on the arms of volunteers over conventionalstockinette, then the casts were wrapped with 7.62 cm Coban® elastomericbandage (available from 3M Company, St. Paul, Minn.) and manipulated toconform to the arms. The casting articles had set after several minutesand were allowed to cure over several hours to form strong, durablecasting articles. The laminated articles cured rapidly and were veryconformable. The cured article's hardened surface reproduced the surfacepattern of the elastomeric bandage, indicating the exceptionalmoldability of the material.

Example 3 Casts Comprising Viscoelastic Resin and Glass Bubbles

A resin was formulated by mixing the ingredients shown in the followingtable as described below.

                  TABLE 3                                                         ______________________________________                                        Component   Equiv. wt.   Parts  Weight (g)                                    ______________________________________                                        Isonate 2143L                                                                             144.4        55.66  222.65                                        MEMPE       129.5         1.53   6.13                                         Terathane 1000                                                                            490          35.46  141.83                                        Arcol LG-650                                                                              86.9          3.35  13.38                                         PVP-360                  4.0    16.00                                         ______________________________________                                    

Solid PVP-360 was added to Terathane 1000 polyol (available from Dupont,Wilmington, Del.) in a ratio of 1 part PVP-360 to 9 parts Terathane in astirred 5000 ml flask. The mixture was heated to 120° C. under a vacuumof 0.7 torr to provide a clear viscous material. The vacuum was helduntil the solution was dry and no further bubbling was evident. Aportion (157.83 g) of this material was added to a homogeneous mixtureof 13.38 g of LG-650 in 222.65 g of Isonate 2143L and the mixture wasstirred and warmed until a clear homogeneous solution resulted. TheMEMPE was added and the mixture was placed on a shaker for one hour in asealed insulated jar. On cooling the resin was elastic, showing asignificant rebound force, and capable of forming a film when placedbetween two gloved hands and the hands slowly separated.

A casting article was prepared in a dry environment (i.e., having lessthan 4% relative humidity) by adding 60 g of Scotchlite™ H50/10,000 EPXglass bubbles (available from 3M Company, St. Paul, Minn.) to 40 g ofthe above resin. The mixture (V_(f) /V_(r) =3.12) was stirred, thenkneaded by hand to provide a homogeneous conformable mixture. Themixture was spread and formed in a 9.53×30.5×0.635 cm teflon mold linedwith a PVA film as described in Example 2 using a teflon coated rollingpin. The article was removed from the mold, the PVA liner was peeled offand discarded. The article was placed flat and stored in an airtightpolyethylene coated aluminum foil pouch.

To determine the usefulness of the article it was removed from the pouch(gloves were not needed) and immersed in a stream of warm tap water forseveral seconds. It was then applied to an arm covered with conventionalcasting stockinette. The article was next overwrapped with a 7.62 cmwide Ace-type elastic bandage and molded to conform to the arm. Thecasting article had set in less than 5 minutes. When the Ace bandage wasremoved to examine the article it was found that excellent conformanceto the arm was obtained. Notably, even the texture of the stockinettewas apparent in the cured molded article. After 24 hours the curedarticle was sufficiently strong and weight bearing that an adultweighing 63 kg could stand on it without breaking it.

Example 4 Casting Article Comprising Glass Bubbles and Various ElasticResins

The following resins were formulated to evaluate their potential for usewith glass bubble fillers.

                  TABLE 4a                                                        ______________________________________                                        Component    Equiv. wt.  Parts   Weight (g)                                   ______________________________________                                        Isonate 2143L                                                                              144.4       52.4    228.45                                       Benzoyl Chloride         0.05    0.21                                         Antifoam 1400            0.17    0.74                                         Ionol                    0.45    1.98                                         MEMPE                    1.09    4.74                                         Pluronic F-108.sup.1                                                                       7250        3.78    16.50                                        PPG-425      212.50      9.88    43.08                                        PPG-725      378.3       26.78   116.76                                       Secondary Polymer.sup.2  5.4     23.54                                        ______________________________________                                         .sup.1 Available from BASF Wyandotte Corp., Parsippany, NJ.                   .sup.2 As described below in Table 4b.                                   

                  TABLE 4b                                                        ______________________________________                                        Polymer #                                                                              Secondary polymer employed.sup.1                                                                 M.sub.w  M.sub.n                                  ______________________________________                                        1        IOA.sup.2 /acrylamide (96/4)                                                                     2,143,100                                                                              178,982                                  2        IOA/acrylamide (93/7)                                                                            1,718,272                                                                              217,321                                  3        IOA/NVP (91/9)     1,940,328                                                                              183,965                                  4        HEMA.sup.3 /butyl methacrylate (30/70)                                                           --       --                                       ______________________________________                                         .sup.1 Described as a ratio by weight of comonomers.                          .sup.2 "IOA" = Isooctyl acrylate.                                             .sup.3 "HEMA" = Hydroxyethyl methacrylate.                               

In order to prepare the resins a solution of the secondary polymer inPPG 725 polyol was first prepared (i.e., the polymers of runs 1, 2, and3 comprising 18-24%; 22-27% and 25-28% solids respectively in a heptaneand ethyl acetate solvent mixture were dissolved in the PPG 725). Thesolvents were then removed by evaporation in vacuo.

Polymer 1 was not soluble in PPG 725, polymer 2 was soluble butprecipitated when resin formulation was attempted, and polymer 3 gave anexcellent elastic resin. Polymer 4 was dissolved and dried in Terathane1000 at 10% by weight by heating under vacuum (0.5 torr) at 100° C. togive a clear solution which was a good candidate for resin formulationin a resin such as that shown in Table 3 of Example 3.

Example 5 Resins for Use With Glass Bubble Fillers

The following resins were formulated to evaluate their potential for usewith glass bubbles. Each mixture was made in an 227 ml jar and mixed ona roller for about 16 hours.

                  TABLE 5                                                         ______________________________________                                        Component  Resin 5-1       Resin 5-2   Resin 5-3                              ______________________________________                                        Isonate 2143L                                                                            125.89  g       113.21                                                                              g     99.89                                                                              g                                 MEMPE      0.0     g       3.5   g     3.5  g                                 PPG-425    74.11   g       83.3  g     97.31                                                                              g                                 NCO/OH ratio                                                                             2.5             2.0         1.5                                    ______________________________________                                    

Resin 5-1 was acceptable with moderate viscosity. Resin 5-2 appeared tobe very viscous and perhaps elastic but very stiff. Resin 5-3 was toohard and stiff to be manipulated by hand.

Example 6 Casting Article Comprising Resin, Glass Bubbles and PolymerFibers

A casting article was prepared by combining 19.9 parts of the resin ofExample 2 with 19.9 parts of the resin of Table 6 and adding 58.8 partsglass bubbles (Scotchlite™ H50/10,000 EPX, available from 3M Co., St.Paul, Minn.) and 2 parts of 1.5 denier 1.9 cm polyethylene terephthalatefibers (available from Minifibers Co., Johnson City, Tenn.).

                  TABLE 6                                                         ______________________________________                                        Component        Equiv. wt.                                                                             Parts                                               ______________________________________                                        Isonate 2143L    144.4    55.66                                               MEMPE catalyst   129.5     1.53                                               Terathane 1000   490      35.46                                               Arcol LG-650     86.9      3.35                                               PVP-360.sup.1             4.0                                                 ______________________________________                                         .sup.1 Predissolved in the Terathane 1000                                

The resins were mixed with Scotchlite™ H50/10,000 EPX glass bubbles and1.5 denier filaments of 1.9 cm length polyethylene terephthalate,spreading the filaments by mixing well. An article was molded in ateflon mold as described in Example 2 first batch except without a PVAliner. The resulting composite was placed flat and stored in aconventional cast pouch of polyethylene coated aluminum

The casting article of the present Example was removed from the storagepouch. Curing was initiated with warm water and a cast was formed on thearm of a volunteer over conventional stockinette, then the cast waswrapped with a 7.62 cm Coban® elastomeric bandage and manipulated toconform to the arm. The casting article had set after several minutesand was allowed to cure over several hours to form a strong, durablecasting article. The article cured rapidly and was very conformable.

Example 7 Casting Article Composites

Several casting materials were formulated using varying amounts of twocasting resins and percent catalyst. Glass bubbles were added to eachresin to provide casting composite articles for property evaluation. Theresins were formulated using the ingredients listed in Tables 7a and 7b.

                  TABLE 7a                                                        ______________________________________                                        Ingredient        Resin A (g)                                                                             Resin B (g)                                       ______________________________________                                        Benzoyl chloride  0.13      0                                                 Isonate 2143L     384.82    389.4                                             MEMPE catalyst    3.14      amount varied                                     DB-100            0.47      1.26                                              Ionol             1.26      3.36                                              Carbowax 600 polyol                                                                             187.31    0                                                 Carbowax 1450 polyol                                                                            112.41    0                                                 PVP-360           10.46.sup.1                                                                             28.0.sup.2                                        Terathane 1000 polyol                                                                           0         285.8                                             Mesitylene sulfonyl chloride                                                                    0         0.56                                              ______________________________________                                         .sup.1 Dissolved and dried in the Carbowax 600                                .sup.2 Dissolved and dried in the Terathane 1000                         

Resin A was prepared in a glass vessel under a stream of nitrogen gas. Awarm (about 49° C.) mixture of polyol and PVP was mixed with the Isonateand the mixture was shaken until uniform dispersion occurred. The otheringredients were added (catalyst last) then the mixture was shakenagain.

Resin B was prepared by adding the warm (49° C.) polyol/PVP-360 mixtureto the Isonate, mixing, then adding the other ingredients in the order:Ionol, DB-100 and Mesitylene Sulfonyl Chloride. The resins were mixedaccording to the proportions listed in Table 7b. The catalyst was addedlast.

The articles were made by hand mixing 40 g of resin (or resins) with 60g of Scotchlite™ H50/10,000 EPX glass bubbles (available from 3MCompany, St. Paul, Minn.) which had been dried by heating at 120° C. forabout 16 hours until a dry to the touch putty-like consistency wasobtained. The batch was split into 2 equal parts and each was placed ina Teflon mold, as described in Example 2, and rolled flat to fit themold using a quart jar. A piece of cheese cloth which had been coatedwith resin as described in Example 1 was sandwiched between the twosheets of composite and the laminate was placed in a Teflon mold and wasrolled together using the quart jar. This article was then stored flatin a polyethylene coated aluminum foil pouch. The articles werecomprised of the following parts as set out in Table 7b:

                  TABLE 7b                                                        ______________________________________                                        Run                                                                           #     Resin A (g)                                                                             Resin B (g)                                                                             Catalyst (%)                                                                          Bubbles (g)                                                                           V.sub.f /V.sub.r                    ______________________________________                                        1     21        22.4      1       63      2.95                                2     0         44        1.2     66      3.04                                3     41        0         1.2     61      3.01                                4     40        0         0.8     60      3.06                                5     0         43        0.8     65      3.09                                6     25        27        1.0     78      3.06                                7     21.73     20.0      1.0     61.8    3.01                                ______________________________________                                    

Each article was then evaluated as follows: Water was put in a 1 gallonbucket at about 25° C. A 35 cm (approx.) piece of 5.08 cm stockinette(3M) was placed over a 5.08 cm steel mandrel. The article was dipped inwater for exactly 10 seconds and pulled out of the water. Each articlewas placed longitudinally on the mandrel and was rubbed by the applierto evaluate the extent of resin movement or "cream level" and handlingproperties for about 30 seconds, and then was overwrapped with an acebandage.

The following properties were evaluated: set time, cream level, andrelative initial cohesive strength. The results are listed below inTable 7c.

                  TABLE 7c                                                        ______________________________________                                                             Cream level                                                                              Initial strength                              Run     Set time (sec)                                                                             (rank 1 to 15)                                                                           (rank 1 to 10)                                ______________________________________                                        1       222.9        10.0       1.0                                           2       153.0         2.0       4.0                                           3       190.9        12.0       3.0                                           4       244.6        10.0       1.0                                           5       145.7         1.0       4.0                                           6       221.0        10.0       1.0                                           7       222.0         4.0       1.0                                           ______________________________________                                    

Set time was the time required for the composite to cure sufficiently tomaintain its shape so that it could no longer be easily shaped by handpressure.

Relative cream level was a subjective measurement of ease and extent ofcomposite redistribution on the surface of the material. This parameteris ranked on a scale of 1 to 15 where 1 represents a material which isnot creamy (i.e., the composition did not move on the surface) and 15represents a material which has a plaster-like composite cream.

Relative initial cohesive strength is a subjective measurement on ascale of 1 to 10 where 1 represents a material which is very weak (i.e.,falls apart during molding) and 10 represents a material which is asstrong as commercially available fiberglass articles such as 3MScotchcast® One-Step Splint measured about 10 minutes after dipping inwater.

It is observed that the fastest set time was obtained with 100% Resin Band at higher concentrations of Resin A set time was increased. Creamlevel increased as percent Resin A increased. Initial strength decreasedas percent Resin A increased (i.e., as the level of polyethylene glycolincreased).

Example 8 Rheology of Resins Comprising Secondary Polymer

A series of eight resins were prepared in order to illustrate the effectof the addition of a soluble secondary polymer on the rheology of theresin and in particular on the tan δ of the resin. The rheology can bequantified by measuring the storage modulus, G', and the loss modulus,G", of the resin. As will become apparent from the examples, amaterial's rheology will be affected by both the concentration ofsecondary polymer added and the molecular weight of the secondarypolymer.

Two different molecular weight PVP polymers were added to awater-curable resin as described below. The first series of resins wereprepared using PVP-360. The PVP-360 was dissolved in Terathane 1000 at aconcentration of 13.5% by weight according to the drying procedure ofExample 2 to form a stock solution ("PVP-T"). Using this stock solutionfive modified resins were prepared according to the followingformulation as described in Tables 8a and 8b:

                  TABLE 8a                                                        ______________________________________                                        Chemical        Eqwt. (g/eq)                                                                            Weight (g)                                          ______________________________________                                        PVP-T                     see below                                           Terathane 1000  490.0     see below                                           Benzoyl chloride          0.16                                                Antifoam 1400             0.36                                                BHT                       0.96                                                Isonate 2143L   144.4     111.26                                              ______________________________________                                    

The PVP/Terathane solution and the Terathane 1000 were added accordingto the following table:

                  TABLE 8b                                                        ______________________________________                                        Resin →                                                                             A       B       C     D     E                                    ______________________________________                                        PVP-T solution (g)                                                                         0       13.75   27.79 42.11 56.73                                Terathane 1000 (g)                                                                         73.08   61.18   49.04 36.65 24.00                                Weight % PVP 0       1       2     3     4                                    ______________________________________                                    

The resin was prepared by adding together the PVP-T solution and theTerathane to a 8 oz. jar (maintained at 49° C.) and mixing thoroughly.Next all of the components listed in Table 8a were added in the orderlisted with mixing for approximately 5 minutes between each addition.The final solution was vigorously shaken for 1 hour then placed in a 65°C. oven overnight to ensure the resin was bubble free. Note that thesesamples do not contain a catalyst. This was done to ensure the resin didnot cure while rheology measurements were being taken. In addition, therheometer's test chamber was continuously purged with nitrogen.

A second set of resins was prepared using 1,280,000 molecular weight PVP(available from ISP Technologies as "K-90" and hereinafter referred toas "PVP-1280"). The PVP-1280 was dried by adding 500 g PVP-1280 to 2000g Carbowax 600. The mixture was placed under vacuum with stirring andheated to 145° C. at a pressure of 0.6 mm Hg. This stock solution,"PVP-C," was held at 145° C. for 1.5 hours and then cooled to 49° C. Theresins were prepared by mixing together the following resin components:

                  TABLE 8c                                                        ______________________________________                                        Chemical   Eqwt. (g/eq)                                                                            Resin F   Resin G                                                                             Resin H                                  ______________________________________                                        Isonate 2143L                                                                            144.4     114       114   114                                      PVP-C                40        58    116                                      Carbowax 600                                                                             310.9     13        0     0                                        Carbowax 1450                                                                            739.1     15.2      15.2  15.2                                     Arcol LHT-240.sup.1                                                                      237.0     14        14    14                                       (Approx. wt. %       4         6     11                                       PVP)                                                                          ______________________________________                                         .sup.1 Polypropylene glycol glycerol started triol.                      

The resins were prepared by mixing the PVP-C solution and Carbowax 600(if used) into the Isonate 2143L, and heating to between about 65° to70° C. The contents were mixed vigorously until the PVP-1280 wasuniformly distributed and a viscoelastic solution resulted. Theremaining polyols were added in the order shown with vigorous mixingbetween additions. Once mixed the resins were sealed and placed in a 65°C. oven for 12 hours to ensure entrapped air bubbles were minimized.Resin H still had some aeration due to its extremely high viscosity.Note that these samples do not contain a catalyst. This was done toensure the resin did not cure while rheology measurements were beingtaken. In addition, the rheometer's test chamber was continuously purgedwith nitrogen.

For purposes of the present invention, the rheology of the resins wasdetermined using a Rheometrics Dynamic Analyzer (RDA-II) in parallelplate geometry. All experiments were done at 25° C. under a dry nitrogenenvironment in a dynamic shear mode where the dynamic strain was keptbelow the linear viscoelastic strain limit (i.e., less than 10%). Thediameter of the plates was varied so as to keep the measured torquewithin the operating limits of the rheometer. The gap between the plateswas less than about one mm. Both the storage modulus (G') and the lossmodulus (G") were measured. The results indicate that over the shearrange of 0.1-100 radians per second the storage modulus is increased byalmost 3 orders of magnitude by addition of as little as 1% of thePVP-360 (resin B). Addition of 11% of the PVP-1280 increased the storagemodulus by almost 7 orders of magnitude over the shear range tested. Acomplete listing of the data appears below in Table 8d.

                                      TABLE 8d                                    __________________________________________________________________________    Resin    A  B  C   D   E   F   G   H                                          __________________________________________________________________________    PVP conc. (˜wt. %)                                                               0  1  2   3   4   4   6   11                                         Mol. wt. (×1000)                                                                 -- 360                                                                              360 360 360 1,280                                                                             1,280                                                                             1,280                                      G' at 0.1 rad/sec.sup.1                                                                0.009                                                                            1.8                                                                              14  28  100 850 2100                                                                              38,000                                     G' at 1 rad/sec                                                                        0.028                                                                            30 180 350 900 4,300                                                                             9,000                                                                             110,000                                    G' at 10 rad/sec                                                                       0.22                                                                             300                                                                              1,300                                                                             2,200                                                                             4,400                                                                             17,000                                                                            29,000                                                                            420,000                                    G' at 100 rad/sec                                                                      6  2,000                                                                            5,600                                                                             10,000                                                                            18,000                                                                            52,000                                                                            88,000                                                                            2,100,000                                  G" at 0.1 rad/sec.sup.2                                                                1  20 75  150 350 1,700                                                                             3,000                                                                             40,000                                     G" at 1 rad/sec                                                                        9  180                                                                              580 900 1,800                                                                             6,000                                                                             10,100                                                                            170,000                                    G" at 10 rad/sec                                                                       98 1,020                                                                            2,900                                                                             3,000                                                                             7,500                                                                             25,000                                                                            40,000                                                                            700,000                                    G" at 100 rad/sec                                                                      950                                                                              7,000                                                                            13,000                                                                            20,000                                                                            30,000                                                                            120,000                                                                           190,000                                                                           3,000,000                                  Tan δ.sup.3 at 0.1 rad/sec                                                       111                                                                              11 5.4 54  3.5 2.0 1.4 1.1                                        Tan δ at 1.0 rad/sec                                                             321                                                                              6.0                                                                              3.2 2.6 2.0 1.4 1.1 1.5                                        Tan δ at 10 rad/sec                                                              445                                                                              3.4                                                                              2.2 1.4 1.7 1.5 1.4 1.7                                        Tan δ at 100 rad/sec                                                             158                                                                              3.5                                                                              2.3 2.0 1.7 2.3 2.2 1.4                                        __________________________________________________________________________     .sup.1 Dyne/cm.sup.2                                                          .sup.2 Dyne/cm.sup.2                                                          .sup.3 Ratio of G"/G                                                     

A series of 7 curable resins were analyzed for yield stress and zeroshear viscosity at 25° C. The first six resins (Resins B to G)correspond to duplicate batches of those resins disclosed above. Resin"I" had the following formulation and was prepared in the same method asresin G.

                  TABLE 8e                                                        ______________________________________                                        Preparation of Resin "I"                                                      Chemical         Eqwt.  Weight (g)                                            ______________________________________                                        Isonate 2143L    144.4  114                                                   PVP-C.sup.1             80                                                    Carbowax 1450           15.2                                                  Arcol LHT-240           14                                                    ______________________________________                                         .sup.1 "PVPC" = PVP/Carbowax 600 solution prepared per Example 8.        

In a similar manner, viscosity versus shear rate data was generatedusing a Rheometric Dynamic Analyzer in parallel plate geometry over arange of shear rates (0.005 sec⁻¹ to 10 sec⁻¹). The zero shear viscositywas calculated from these curves using the following method. The shearstress at the onset of shear thinning was used as a starting stress forconstant shear experiments in the Rheometrics Stress Rheometer. Aconstant stress was applied for 200 seconds, and the recoverable strainwas monitored for 1000 seconds. If there was no recoverable strain, thestress was deemed to be too high and if there was 100% recoverablestrain the stress was deemed too low. Using this trial and error methodthe proper stress was obtained. In addition, a stress mmp experiment wasdone using a stress range from 0-10,000 dyne/cm² for 1000 seconds. Thelowest stress where a measurable strain was observed was defined as theyield stress. The results are listed in Table 8f.

                  TABLE 8f                                                        ______________________________________                                        Sample  Yield Stress (dyne/cm2)                                                                      Zero Shear Viscosity (Pa s)                            ______________________________________                                        B       10             12.5                                                   C       15             55.0                                                   D       35             118.0                                                  E       40             156.5                                                  F       600            842.0                                                  G       16,000         18,500                                                 I       18,000         41,200                                                 ______________________________________                                    

Example 9 Air Flow Through a Cured Composite

One advantage of the composites of the present invention is theirrelatively high porosity which allows the cast to "breathe" during wear.The breathability of a series of composites which were produced usingvarious microspheres at different concentrations was characterizedaccording to the following test.

A. W. & L. E. Gurley Densemeter Model 4110 (Troy, N.Y.) attached to aGurley-teledyne sensitivity meter (Cat. No. 4134/4135--used forcalibration) and an Engler Instruments Co. Model 605 timer was used tomeasure the flow of air through a composite specimen. Specifically, thisinstrument measured the time in seconds required to pass 10-50 cc of airthrough a 6.45 sq cm piece of 0.64 cm thick cured composite. The testwas performed in a room having a temperature between 23° and 25° C. andabout 50% relative humidity.

The samples were prepared in the following manner. In the center of bothsides of a 5 cm×5 cm square piece of cured composite (0.64 cm thick) wasadhered a 2.54 cm diameter circular piece of Microfoam tape (3M Company,St. Paul, Minn.). Next, the entire sample (top, bottom, and sides) wassealed using Dew Corning 732 RTV multipurpose silicone sealant (Midland,Mich.). The samples with sealant were allowed to cure overnight. Oncecured the microfoam tape circles were gently removed using a tweezers toleave a 2.54 cm diameter circular opening through which air could bepassed.

The top surface was then covered with a piece of Scotch Brand #471yellow plastic tape (available from 3M Co., St. Paul, Minn.) which had amating 2.54 cm diameter hole. Initially the bottom surface was coveredwith a piece of Scotch Brand #471 yellow plastic tape (without a holetherein).

The sample was then tested for its leak rate, i.e., the rate at whichair leaked through imperfections in the seal and/or sealant layer. Theleak rate ("L" in cc/sec) of the sample was determined by placing thesample in the Densometer and measuring the air flow, i.e., the timerequired to pass a known volume (e.g., 10 to 50 cc) of air. Next thelower occluded layer of tape was replaced with a layer of tape identicalto that on the top of the sample except that a 2.54 cm diameter hole wascut and aligned with the sample hole. The air flow rate through thesample and sealant was measured as previously described ("F" in cc/sec).By subtraction the air flow through the sample was then determined bythe following formula: actual sample air flow=F-L (cc/sec). The numbersreported below are an average of two samples. Preferably, an average ofat least 5 samples is utilized.

Composite samples were prepared using the resin of Example 3. The resinwas mixed with various fillers, using the procedure of Example 3 and asdescribed in Table 9 to produce samples approximately 0.64 cm thick. Thesamples were immersed in 25° C. water and allowed to cure for at least24 hours prior to testing. In addition, a commercially available 15layer plaster splint (Orthopedic Casting Laboratories--without paddinglayers available from Worldwide Management Corp., Eudora KS) (Run #6)and an 6 layer slab of Scotchcast Plus Casting tape (Run #7) weretested. The following air flow results were found:

                  TABLE 9                                                         ______________________________________                                        Run # Filler      Weight %   Flow (cc/sec)                                                                          V.sub.f /V.sub.r                        ______________________________________                                        1     3M A16150   50         10.7                                             2     3M A161500  55         14.5                                             3     3M B3712000 55         13.2                                             4     3M K-1      65         3.4                                              5     Dicaperl HP-900                                                                           67         7.7      6.40                                    6     OCL Plaster --         0.04                                             7     3M Scotchcast ™                                                                        --         1028                                                   Plus (6 layers)                                                         ______________________________________                                    

For materials with a high air flow value it may be necessary to eitherincrease the volume of air passed, e.g., 300 cc, or decrease the surfacearea which is open to air flow. However, if the circular opening isreduced the air flow value must be corrected, i.e., normalized to anequivalent air flow per unit area, prior to comparing samples. Forexample, if a sample was prepared with a 1.27 cm circular hole in placeof the 2.54 cm circular hole described above the air flow obtained wouldbe multiplied by 4 to yield a proper comparison.

Example 10 Rate of Dissolution of Various Water-Soluble Films

The time required to "dissolve" a water soluble film is characterized inaccordance with the following test method. A single layer of film is cutand secured between the top and bottom halves of a Millipore FilterHolder (Part #4 but without its standard filter screen--Millipore Corp.,Bedford, Mass.) to provide a 3.5 cm diameter piece of film secured inplace. Twenty milliliters of water is gently added to the top of thefixture (creating approximately a 2 cm head atop the film) by pouringthe water down the side of the fixture. The time for the water todissolve the film and "break-through" the film (i.e., flow through thefilm) is recorded. Dissolution time is recorded as the meanbreak-through time of ten samples and is reported below in Table 10a.

                  TABLE 10a                                                       ______________________________________                                                                     Dissolution                                                                           Dissolution                                                  Thickness                                                                              time (sec)                                                                            time (sec)                               Run   Film          (micron) Undried film                                                                          Dried film.sup.4                         ______________________________________                                        1     QSA 2004.sup.1                                                                              38       12.5    24.9                                     2     QSA 2004      51       23.5    50.3                                     3     QSA 2000.sup.1                                                                              38       21.3    47.2                                     4     QSA 2000      51       37.0    96.1                                     5     Aicello Solublon SA.sup.2                                                                   17        2.7     3.7                                     6     EM1100.sup.3  53       22.3    49.9                                     ______________________________________                                         .sup.1 Available from Glenn Corp., St. Paul, Minn.                            .sup.2 Available from Mitsui Plastics Inc., White Plains, NY.                 .sup.3 Hydroxypropylmethylcellulose (CAS No. 00900465-3) available from       Glenn Corp., St. Paul, Minn.                                                  .sup.4 Dried for 20-24 hours at 100° C.                           

The above test yields a good approximation of the time required fordissolution of a film. However, as an alternative embodiment of thepresent invention one may choose to forego use of a separate film ofliner and instead directly laminate the casting material with awater-soluble liner material. This liner film may be difficult, if notimpossible, to later separate from the casting material and test inaccordance with the above method. To test these liner materials it isacceptable to either employ a functional test (i.e., directly measurethe casting tape under conditions of use and measure the time requiredfor the liner to provide a lubricating effect or allow layer-to-layeradhesion of the casting material) or a modification of the above"break-through" test. For example, one may directly form the liner filmagainst the millipore filter (with the same thickness as found on thecasting material) and then conduct the break-through test.Alternatively, one may form the liner film against any other suitableporous substrate and place the laminate in the millipore apparatus fortesting as described above.

Example 11 Moisture Vapor Transmission Through a Casting Material

The moisture vapor transmission of various casting materials is measuredusing the following test. A ring of casting material measuring between 5and 10 cm high and having a 5.08 cm inner diameter is formed by curingthe material against a stockinet covered mandrel. Alternatively, thering may be formed by gluing together two fully cured half rings (i.e.,"C" shaped sheets having an inner radius of 2.54 cm) using a waterimpermeable sealant. Prior to testing, the casting material is allowedto cure for 24 hours. The surface area of the cylinder (A) is taken asthe inner circumferential area, less any areas (such as seam areas)which were occluded with sealant. The average thickness of the castmaterial is also recorded (T). For comparison purposes the averagethickness of the casting material being tested should preferably be thatthickness which provides a comparable ring strength (as described incolumn 15 of U.S. Pat. No. 4,705,840) to 6 layers of 3SM Scotchcast™Plus casting tape, i.e., approximately 90 N/cm width (±45 N/cm width).

The cylinder of cast material is then sealed completely around its lowercircumference to a lower petri dish using a silicone sealant such asSilastic RTV silicone dealant No. 732 (available from Dow Corning Co.,Midland Mich.). The sealant is allowed to cure for 24 hours. A 25 mlbeaker of deionized water is placed inside the cylinder and on top ofthe lower petri dish. Care is taken to not spill the water from thebeaker. The top of the cylinder is then closed by sealing a second petridish on the top circumference using the aforementioned RTV sealant. Thesealant is allowed to cure for 12 hours.

The total weight of cast material, petri dishes, beaker, and water isrecorded. The samples are then placed in a 37.8° C. oven having arelative humidity of between 24 and 30 percent. The samples are removedperiodically and weighed. The weight loss per unit time is calculated asthe slope of the weight loss vs. time plot. The slope may be calculatedusing a least squares line fitting method if desired. The results areexpressed as the slope of the weight loss vs. time divided by the area,A, of the cast material. The "moisture vapor transmission" is expressedin units of g water lost/day/sq cm.

The seven samples described in Example 7 along with the three samplesdescribed in Example 14 were tested for moisture vapor permeability.These samples were compared to a traditional plaster of Paris materialand a traditional synthetic fiberglass material. The plaster of Parismaterial was Synthetic Plus™ Plaster (cat. no. 4900-03 available fromDepuy Co., Warsaw, Ind.). The fiberglass material was Scotchcast™ Plus(available from 3M Co., St. Paul, Minn.). For the fiberglass and Plastersamples two replicates were run. For the samples of this invention onlyone sample was available. Preferably an average of 3 to 5 samples wouldbe recorded.

                  TABLE 11a                                                       ______________________________________                                                                Vapor transmission                                    Run   Sample            (g water lost/day/sq cm)                              ______________________________________                                        1     Example 7 run 1   0.196                                                 2     Example 7 run 2   0.253                                                 3     Example 7 run 3   0.248                                                 4     Example 7 run 4   0.160                                                 5     Example 7 run 5   0.178                                                 6     Example 7 run 6   0.176                                                 7     Example 7 run 7   0.201                                                 8     Scotchcast Plus (6 layers)                                                                      0.413                                                 9     Plaster: Synthetic Plus ™ Plaster                                                            0.185                                                       (Depuy)(15 layers)                                                      10    Example 14 run 1  0.110                                                 11    Example 14 run 2  0.195                                                 12    Example 14 run 3  0.268                                                 ______________________________________                                    

Example 12 Strength Testing--Three Point Bend and Tensile Methods

The flexural strength and modulus of several materials of the presentinvention were compared to two traditional casting materials (plaster ofParis and a synthetic fiberglass casting material). As shown below inTable 12d the materials of the present invention compare favorably tothese traditional materials. In order to make this comparison sampleswere prepared and tested for flexural strength and flexural modulususing a modified version of ASTM test method number D790-91 entitled:"Standard Test Methods for Flexural Properties of Unreinforced andReinforced Plastics and Electrical Insulating Materials".

Seven resin compositions were made which had varying amounts of asecondary polymer component (of varying molecular weights) as describedin Tables 12a and 12b. To these resins were added glass bubbles(Scotchlite™ H50/10000 EPX) at a concentration of 60 percent by weightfiller. The composite materials (V_(f) /V_(r) =3.1) were made intosplints according to the general procedure of Example 7.

                  TABLE 12a                                                       ______________________________________                                        Chemical       Eqwt. (g/eq)                                                                            Resin A Resin B                                                                             Resin C                                ______________________________________                                        Isonate 2143L  144.4     228     228   228                                    Secondary polymer solution.sup.1                                                                       132.5   88.0  45.0                                   Carbowax 600   301.9     0             70.0                                   Carbowax 1450  739.1     30.4    30.4  30.4                                   Arcol LHT-240  237.0     28.0    28.0  28.0                                   Benzoyl Chloride         0.2     0.2   0.2                                    Antifoam 1400            0.72    0.72  0.72                                   BHT                      1.92    1.92  1.92                                   MEMPE                    4.8     4.8   4.8                                    ______________________________________                                         .sup.1 20% by weight solution of either: PVP360 (having 360,000 molecular     weight and available from Aldrich Chemical Co.); PVP1280 (having 1,280,00     molecular weight and available from ISP Technologies) dissolved in            Carbowax 600 (available from Union Carbide Co.); or a 1:1 blend of these      solutions as described in Table 12b.                                     

                  TABLE 12b                                                       ______________________________________                                        Resin No.                                                                              Resin     Secondary polymer                                          ______________________________________                                        12-1     A         PVP-360                                                    12-2     C         PVP-360                                                    12-3     B         1:1 Blend of PVP-360 and PVP-1280                          12-4     B         1:1 Blend of PVP-360 and PVP-1280                          12-5     A         PVP-1280                                                   12-6     B         1:1 Blend of PVP-360 and PVP-1280                          12-7     C         PVP-1280                                                   ______________________________________                                    

In addition, several splints were made using the resin described belowin Table 12c (hereinafter referred to as Resin 12-8) and 65% by weightScotchlite™ H50/10000 EPX glass bubbles (3M Company), resulting in acomposite having a V_(f) /V_(r) =3.9.

                  TABLE 12c                                                       ______________________________________                                        Chemical         Eqwt. (g/eq)                                                                            Weight (g)                                         ______________________________________                                        Isonate 2143L    144.4     228                                                PVP-Carbowax 600.sup.1     122.5                                              Carbowax 1450    739.1     30.4                                               Arcol LHT-240    237.0     28.0                                               Benzoyl Chloride           0.2                                                Antifoam 1400              0.72                                               MEMPE                      4.8                                                ______________________________________                                    

The splints were made in an atmosphere of less than 4% relative humidityby rolling the fully homogenous composition into a 9.53×30.5×0.635 cmteflon mold. No scrim was placed in the materials. The composite splintswere stored flat in sealed aluminum foil pouches until use.

The splints were evaluated during the cure process. All samples wereobserved to provide acceptable splinting materials and had set timesbetween 136 and 214 seconds. In general, samples which contained highermolecular weight secondary polymer and higher concentrations ofsecondary polymer exhibited higher cohesive strength.

The samples were cured by immersion in 25° C. water followed by moldingthe materials as a flat sheet or laminate and then storing the materialsat 25° C. and 50% relative humidity. Each material was immersed in thewater for 10 seconds without agitation. For the sheet materials of thepresent invention the material was simply allowed to cure in a flatstate. For the plaster of Paris sample (OCL Roll Form Splint, 15 layersof plaster) the outer padding was first removed. The fiberglass sample(Scotchcast™ Plus available from 3M Co., St. Paul, Minn.) was formedinto 6 and 8 layer laminates. Once removed from the water, the plasterof Paris and fiberglass samples were compressed slightly by hand andrubbed to promote layer to layer lamination. Preferably, a minimum of 5samples were tested and the mean reported. However, in some cases only 2samples were tested. Once cured the samples were cut to 9.53 cm longstrips. The width of the samples of the present invention were 9.6 cm.The width of the 3M Scotchcast Plus samples were 8.5 cm. The width ofthe plaster of Paris samples were 6.86 cm. The samples were allowed tocure overnight in a room maintained at 25° C. and 50% relative humidityprior to testing for strength.

The flexural strength and flexural modulus values for these samples arelisted in Table 12d. Sample numbers 12-3 and 12-7 were not tested. Eachsample was placed in a fixture and the fixture properly centered in aproperly calibrated Instron™ 1122 testing machine (Instron Corp., ParkRidge, Ill.). The fixture was a three point bend device in which thesupports were cylindrical rods (1.91 cm in diameter and 13.7 cm long).The supports were parallel to one another and spaced 7.62 cm apart(measuring from the centerline). The load was applied through a similarcylinder positioned above the sample at the midpoint of the supportcylinders. Compression loads were applied to the flat sample at themidpoint of the sample using a crosshead speed of 2.54 cm per minute.

The flexural strength ("S") was calculated using the following formula:S=3 FL/2 bd² where: F=maximum load (N); L=support span (in thiscase=7.62 cm); b=width of sample (cm); and d=sample thickness (cm). Theflexural modulus ("E_(b) ") was calculated using the following formula:E_(b) =m(L³ /4 bd³) where, L, b, and d are as defined above and m is theslope of the load displacement curve.

                  TABLE 12d                                                       ______________________________________                                                        Flexural strength                                                                         Flexural modulus                                  Sample No.      (N/cm.sup.2)                                                                              (N/m.sup.2)                                       ______________________________________                                        12-1            1006        10.5                                              12-2            824         5.64                                              12-4            1837        10.2                                              12-5            1764        7.42                                              12-6            976         4.00                                              12-8            918         5.20                                              Plaster-15 layers                                                                             1199        11.7                                              3M Scotchcast Plus - 8 layers                                                                 655         1.94                                              3M Scotchcast Plus - 6 layers                                                                 1172        7.95                                              ______________________________________                                    

Two uncured samples were prepared in the form of 25.4 mm wide sheets andtested for their tensile strength. Samples were conditioned in a sealedpackage at 23°-25° C. for at least 24 hours prior to testing. Eachsample was placed in the pneumatic jaws of a properly calibrated Instron1122 testing machine (Instron Corporation, Park Ridge, Ill.) equippedwith Sintech Test Works™ material testing software (Sintech, Stoughton,Mass.). The jaws were equipped with a metal spacer to prevent crushingof the sample (i.e., the sample should be held by the jaws with enoughforce to resist slippage during testing but not so much force that theuncured material is crushed to the point of breaking. The jaw spacingwas 2.54 cm and the samples tested were 2.54 cm wide×7.62 cm long andwere cut from length direction of the casting material such that thetensile direction corresponded to the direction in which the principleload would be applied during actual application of the products. Thecrosshead speed was set at 2.54 cm/min. Peak load to failure per unitwidth of sample is reported below in Table 12e. All materials weretested immediately after removal from the storage pouch, i.e., beforebeing cured and without dipping in water. Preferably an average of atleast 5 samples is reported.

                  TABLE 12e                                                       ______________________________________                                        Sample No.   Tensile strength (N/mm)                                          ______________________________________                                        12-2         0.149                                                            12-7         0.119                                                            Cheese cloth 0.520                                                            Plaster of Paris                                                                           0.870                                                            ______________________________________                                    

Example 13 Bulk Density of a Filler

The bulk density of several fillers was measured according to thefollowing test method. A 25 ml graduated cylinder was filled with thefiller sample and vibrated lightly for 5 minutes. After this time thevolume of filler (i.e., as read from the graduations on the side of thecylinder) was recorded. The weight of filler was determined bysubtracting the weight of the cylinder from the total weight of thecylinder and filler. The bulk density is reported as the weight/unitvolume of filler (g/cc).

Example 14 Void Volume Measurement

The void volume of a cured composite was determined by the followingtest method. A sample of a cured composite of known volume ("V_(c) ")and weight ("W_(c) ") is fully submerged in a pan containing a solvent.Suitable solvents for this purpose include solvents which have arelatively low surface tension yet do not cause rapid swelling,dissolution, or disintegration of the composite. In this exampleisopropyl alcohol ("IPA") was found to be suitable and was used. Thesample is submerged in the solvent using any suitable device (such as asmall weight) and then placed in a vacuum chamber. In this example a 73g weight was used to submerge a sample measuring approximately 10.16cm×8.89 cm×0.635 cm. Care was taken to minimize the area of contactbetween the weight and sample so as to not prevent absorption of thesolvent into the sample.

The submerged sample was placed in a vacuum chamber and a vacuum waspulled to a pressure of 125 mm Hg. The vacuum was held for approximately2 minutes, however, longer times may be necessary to ensure completeabsorption of the solvent into the sample's pores. The sample wasremoved from the chamber and residual solvent was removed by quicklyblotting the sample with a Premiere™ (Scott Paper Company, PhiladelphiaPa.) paper towel. The weight of the IPA impregnated sample ("W_(cs) ")was then recorded. Preferably at least 5 samples are analyzed and themean absorption weight is calculated. The weight of absorbed solvent("W_(s) ") is calculated by subtraction (W_(s) equals W_(cs) minusW_(c)) and converted to volume ("V_(s) ") using the density relationshipfor that solvent (i.e., 0.785 gm/ml for IPA). The volume of absorbedsolvent (i.e., the void volume of the composite) is then expressed as aratio of the volume of the cured composite (V_(s) /V_(c)) or as apercentage of the volume of the cured composite (% void volume equals100 times (V_(s) /V_(c))).

The void volume was measured on three cured composite materials. Thematerials were formed into 30.5 cm×8.9 cm×0.64 cm slabs using the resindescribed in Table 14a and various levels of 3M H50/1000 EPX glassbubbles as described in Table 14b and then cut to a length of 10.16 cmfor testing. The resin and splints were made according to the generalprocedure of Example 7. Notably, the composite's volume did notsignificantly change during cure.

                  TABLE 14a                                                       ______________________________________                                        Chemical          Eqwt. (g/eq)                                                                            Weight (g)                                        ______________________________________                                        Isonate 2143L     144.4     228                                               Secondary polymer solution.sup.1                                                                          122.5                                             Carbowax 1450     739.1     30.4                                              Arcol LHT-240     237.0     28.0                                              Benzoyl Chloride            0.2                                               Antifoam 1400               0.72                                              MEMPE                       4.8                                               ______________________________________                                         .sup.1 13.5% by weight solution of PVP360 (available from Aldrich Chemica     Co. and having a 360,000 molecular weight) dissolved in Carbowax 600          (available from Union Carbide Co. and having an equivalent weight of 301.     g/eq).                                                                   

                  TABLE 14b                                                       ______________________________________                                                                      Vol.                                                                          Uncured                                                Filler Filler          Composite                                                                            Void vol.                                Sample (g)    (bulk vol)                                                                             Resin (g)                                                                            (ml)   (%)    V.sub.f /V.sub.r                  ______________________________________                                        14-1   60     194      40     195    19.7   3.12                              14-2   65     216      35     1215   24.5   3.86                              14-3   70     295      30     1220   24.0   4.85                              ______________________________________                                    

Example 15 Composite Comprising a Thermoplastic Binder

A solution of Tone 787 polycaprolactone polymer (available from UnionCarbide and reported to have a molecular weight of 80,000) was made bydissolving 220 g polymer in 500 g toluene and gently agitating for 24hours. After this time an additional 75 g toluene was added and mixedand the contents warmed to 65° C. to produce a clear viscous solutionwhich contained 28% by weight polycaprolactone.

In a one liter beaker containing 45 g Scotchlite™ H50/1000 glass bubbles(3M Co., St. Paul, Minn.) was added 85.7 g of the above solution. Thiswas initially mixed using a tongue depressor and then later kneaded byhand. As the material became tacky an additional 16 g bubbles were addedand the mixture kneaded. The final composition was only slightly tacky.This was rolled into a 7.6 cm×30.5 cm×0.64 cm mold and set in a fumehood for several hours to allow the toluene to begin evaporating. Thematerial was then placed in a 48° C. oven for approximately 14 hours toensure all the toluene had evaporated.

A smooth porous composite resulted. The void volume was measuredaccording to the method in Example 14 and found to be 34.65%.

The material was immersed in a 70° C. water bath for 5 minutes andmolded around a wrist. The material was observed to be very conformable.The cast's strength was just adequate for immobilization of a wrist butwould be suitable for lower load applications such as finger splints andthe like.

Example 16 Composite Comprising a Thermoplastic Binder

A solution 31 percent by weight Tone 787 in toluene was produced bymixing 220 g Tone into 490 g toluene and mixing gently for 24 hours(Solution "16A"). The solution was heated to 65° C. for 7 hours to forma clear viscous homogenous solution. The polymer solution was mixed withglass bubbles, formed into a mold, and the toluene evaporated asdescribed in Example 15. The following amounts of filler and polymersolution were used:

                  TABLE 16a                                                       ______________________________________                                        Sample       Solution 16A (g)                                                                          Filler (g)                                           ______________________________________                                        16-1         90          45.5                                                 16-2         90          56.6                                                 ______________________________________                                    

Notably both samples were observed to be quite tacky and were pouredinto the molds. The materials were allowed to sit for several minutesprior to rolling to allow residual toluene to evaporate.

After allowing for complete evaporation of the solvent the materialswere pressed into a 0.5 cm thick slab using a heated Dake flat plattenpress (Model 44027, Dake Inc. Grand Haven Mich.). The plattens wereheated to 77° C. The samples were placed between two pieces of siliconecoated release liner and pressed under very low pressure forapproximately 1 minute to allow the sample to heat up. The pressure wasthen increased to approximately 4000 psi and released. Next both sidesof the hot sample were dusted with additional glass bubbles and thematerial pressed again in the same manner but this time only to apressure of approximately 1000 psi. The additional glass bubbles on theouter surface allowed the slab to be heated on a hot plate to a moltencondition without sticking to the hot plate.

The samples were applied to a wrist by heating the sample in a warmwater bath. Both samples B and C were molded to a wrist and hadsufficient integrity to be used as a splint immobilization device.

Example 17 Composite Comprising Resin Having Increased NCO/OH Ratio

Three resins were prepared in 454 ml glass jars using the followingcomponents in grams:

                  TABLE 17a                                                       ______________________________________                                                 A           B           C                                            Chemical (NCO/OH) = 3.1                                                                            (NCO/OH) = 3.5                                                                            (NCO/OH) = 3.9                               ______________________________________                                        Isonate 2143L                                                                          217         228         239                                          Benzoyl  0.26        0.26        0.26                                         Chloride                                                                      DB-100   0.66        0.66        0.66                                         BHT      1.76        1.76        1.76                                         MEMPE    5.12        5.12        5.12                                         Carbowax 1450                                                                          50          46          43                                           Carbowax 600                                                                           60          51          44                                           Secondary                                                                              83          83          83                                           polymer                                                                       solution.sup.1                                                                ______________________________________                                         .sup.1 The secondary polymer solution is a 20% by weight solution of          polyvinylpyrrolidone (available as "K90" from ISP Technologies Inc., New      Milford, CT) in Carbowax 600. This solution was prepared as follows: 729      grams of K90 PVP was added to 2800 grams of Carbowax 600 at 40° C.     in a 5 liter roundbottom flask fitted with a thermometer and overhead         stirrer. A vacuum of 1 mm Hg was applied as the temperature was gradually     raised to 110° C. This temperature was maintained for 4 hours unti     bubbling had ceased. The highly viscous liquid was then poured while stil     warm into four liter jars and stored in a 49° C. oven.            

Resins "A", "B", and "C" were prepared according to the followinggeneral procedure. The 20% PVP/Carbowax 600 solution and the Isonatewere mixed and gently heated with a heat gun and placed in a mechanicalshaker for approximately 10 minutes until they became homogenous. Nextthe BHT, benzoyl chloride, and DB-100 were added and shaken for anadditional 5 minutes in the mechanical shaker. The Carbowax 600,Carbowax 1450, and MEMPE were then added to the jars and placed in theshaker for another 10 minutes. The jars were placed in a 65.6° C. ovenfor 45 minutes, capped, and rolled slowly for several hours.

To 40 grams of each resin was added 60 grams of 3M Scotchlite™H50/10,000 EPX glass bubbles. A homogeneous composite was obtained(V_(f) /V_(r) =3.1(by kneading the filler into the resin by hand forseveral minutes. Each of the composites were formed into 0.6 cm thicksheets approximately 7.6×30 cm by use of a hydraulic press with 0.6 cmspacers. A maximum pressure of 52 MPa was used to make the sheets. Thesheets were sealed in water impervious aluminum foil pouches until use.The sheets were removed from the pouches and immersed in a water bathfor 5 seconds and placed over a mandrel. The composite from resinformulation A was very soft and moldable while the composite from resinformulation B was very creamy and had a consistency approaching that ofplaster. The composite from resin formulation C was extremely creamy andmoldable and was fluid-like similar to plaster of Paris. All materialshardened after several hours to give rigid splints.

Example 18 Thin Sheet Composite Comprising PVP Modified Resin

A solution (designated as part "D") was prepared by mixing 328 grams ofIsonate 2143L, 0.72 grams benzoyl chloride, 1.02 grams DB-100, and 2.76grams of BHT in a one liter glass jar. A second solution (designated aspart "E") was prepared by mixing 24 grams of undried PVP (available as"K-120" from ISP Technologies, Inc.) and 153 grams of warm Carbowax 600in a one liter glass jar and placing the jar in a 65.6° C. oven for 2.5hours. To this mixture was added 44 grams of Carbowax 1450 and 40 gramsof Arcol LHT-240. The jar was placed in a mechanical shaker for 5minutes then placed back in the oven for 30 minutes. 6.6 grams of MEMPEwas added and the jar placed in the mechanical shaker for an additional2 minutes then stored in the 65.6° C. oven.

A resin was made by mixing 139 grams of part D with 111 grams of part Ein a 1 liter beaker. This mixture was stirred thoroughly using a highshear mixer (Premier Mill Corp., Reading, Pa.) for approximately 3minutes. An exotherm was observed as well as some gas evolutionindication possible chain extension of the prepolymer. 200 grams of thisresin was placed on 300 grams of K-46 glass bubbles (having a specificgravity of 0.46 and available as Scotchlite™ from 3M Co.) in a 4.5 litermetal mixing bowl and a composite was formed by mixing with a Hobartmixer fitted with a sigma blade for approximately 5 minutes. Thecomposite (V_(f) /V_(r) =3.4) was then formed into a flat rectangle andplaced in a nip roller (comprising adjustable dual-driven rubber coatedrollers having a 5 cm diameter and being 30.4 cm long) until a sheet8.25 cm by about 3.8 cm was formed. The composite was pressed further to0.15 cm thickness by passing it several times through a pasta maker(Atlas™, OMC Marcato Co., Campodarsego, Italy). Finally, the compositesheet was pressed through the pasta maker at a 0.127 cm gap with aporous polyester knit mesh fabric (style 6302 from Gehring Textiles,Inc., New York, N.Y.) of like dimensions. This tape was then rerolled ona plastic core and stored in a water-proof pouch until use. Forevaluation as a casting tape the roll was then immersed in a 23° C.water bath for 10 seconds and rolled around a mandrel. The materialunwound easily and was easily molded. Upon hardening the tape provided arigid cast.

Example 19 Use of Isooctyl Acrylate/N-vinylpyrrolidone Copolymers in aComposite Tape

An isooctylacrylate and N-vinyl-2-pyrrolidone copolymer was producedaccording to the following procedure. To a 1 liter narrow-mouthed bottlewas added 275.0 grams ethyl acetate, 168.75 grams isooctyl acrylate,56.25 grams N-vinyl-2-pyrrolidone, and 0.3375 gramsazobisisobutryonitrile. The contents were deoxygenated by purging thebottle for two minutes with nitrogen at a flow rate of one liter perminute. The bottle was sealed and placed in a rotating water bath toeffect essentially complete polymerization. Additional solvent (100 gmMeOH and 100 gm ethyl acetate) was added to produce a 30% solidssolution. A 1000 gram aliquot of the above copolymer (comprising a 3:1weight ratio of IOA to NVP) at 30% solids in ethyl acetate/methanol wasstripped of solvent by first adding 900 grams of PPG 725 in a 3 literflask fitted with a thermometer and condenser. The contents were heatedto 125° C. for several hours and the solvent collected. The last tracesof solvent were removed under vacuum (1-2 mm Hg) at room temperature for16 hours. This gave a final solution that was 25% IOA/NVP in PPG 725. Asolution (designated as part "F") was prepared by adding to a 4.5 literjar 2730 grams of Isonate 2143L, 4.8 grams of benzoyl chloride, 8.7grams of DB-100, and 23.1 grams of BHT. A second solution (designated aspart "G") was prepared by mixing 60 grams of PPG 2025, 116 grams of PPG725, 85.5 grams of LHT-240, and 361 grams of the IOA/NVP/PPG 725solution from above. The mixture was placed in a 65.6° C. oven for 10minutes, then placed in a mechanical shaker until it became homogeneous.To this solution was added 15.6 grams of MEMPE and the mixture wasagitated for an additional 10 minutes.

In a dry room was mixed 147 grams of part F with 128 grams of part G ina 1 liter beaker with a hand-held electric mixer (Handy Mixer™, Blackand Decker, Shelton, Conn.) for 3 minutes at high speed. 245 grams ofthis mixture was poured onto 300 grams of K-46 3M glass bubbles(pre-dried in an oven at 125° C. for 3 days) in a 4.5 liter metal mixingbowl. The mixture was then made homogeneous by mixing with a Hobartmixer fitted with a metal sigma blade for 2 minutes. The composite(V_(f) /V_(r) =2.8) was stored in a water-proof pouch overnight untiluse. The next day a portion of the composite was calendered intoapproximately 0.254 cm thick sheets using a nip roller (comprisingadjustable dual-driven rubber coated rollers having a 5 cm diameter andbeing 30.4 cm long. The resulting 7.6 cm by 1.8 m sheet was laid out ona table, dusted lightly with K-46 glass bubbles, and the surface lightlypressed with the edge of a tongue depressor (14.6×1.7 cm, BaxterHealthcare Corp., McGaw Park, Ill.) across the width of the tapeapproximately 1 cm apart and to a depth of about 0.12 cm. The sample wasthen rerolled and stored in a water-proof pouch until use. Forevaluation as a casting tape, the sheet was removed from the pouch,immersed in 23° C. water for 10 seconds, and wound around a mandrel. Thematerial was found to be wetted thoroughly throughout the roll. Inaddition, the material could be stretched, had good integrity, and wasvery moldable. The composite hardened in 5 minutes to give a rigid cast.

Example 20 Composite Tape Comprising a Light-weight Scrim

In a 1 liter beaker was added 147 grams of part F and 128 grams part G(both from example 19). The solution was mixed vigorously for 3 minutesusing a high shear mixer, then poured over 300 grams of pre-dried K-46glass bubbles. The material was homogenized using a Hobart mixer asdescribed in example 19. At this point, the composite (V_(f) /V_(r)=2.5) had little integrity. Portions of it were sprinkled onto a 8.25 cmwide scrim of a light-weight web (comprising 1.75 denier polyesterstaple fibers 3.8 cm in length at 6 grams/m² coated with Roplex B15resin from Rohm & Hass Co. at 2 grams/m²). The web with composite wasthen calendered through a nip roller (comprising steel rollers having a7.6 cm diameter and being 22 cm long and coated with a PC-915 plasmacoating, Plasma Coating Co., Bloomington, Minn.) with another layer ofweb so that the resulting composite was sandwiched evenly between thetwo layers of web. The resulting sheet, approximately 0.15 cm thick, wasrerolled, and stored in a water-proof pouch until use. For evaluation asa casting tape, the roll was immersed in a 23° C. water bath for 10seconds while water was squeezed into the roll. The material was thenwound around a mandrel. The material was very conformable and moldableand gave a rigid cast in 10 minutes.

Example 21 Composite Tape Comprising a Hydrophilic Polyol and ExhibitingIncreased Smoothability

A solution (designated as part "H") was prepared by mixing 320 grams ofa secondary polymer solution (described below) with 167 grams ofCarbowax 600 in a 2 liter jar and placing it in a mechanical shakeruntil it became homogeneous. 121.5 grams of Carbowax 1450 was added andhomogenized by shaking followed by 112 grams of Arcol LHT-240 and 21grams of MEMPE. The mixture was placed in a 65.6° C. oven for 45minutes, agitated in the mechanical shaker for 15 minutes, then storedin a 48.9° C. oven for later use. The secondary polymer solution wasprepared by heating a mixture of 3020 grams of Carbowax 600 and 786grams of PVP K-90 in a 5 liter flask at 1-2 mm Hg for 16 hours withgentle stirring.

A second solution (designated as part "I") was prepared by mixing 20grams of PPG 2025, 69.5 grams of PPG 725, 28.5 grams of Arcol LHT-240,5.2 grams of MEMPE, and 85 grams of a 30% IOA/NVP/PPG 725 solution in a454 ml jar. The solution was homogenized using a mechanical shaker andstored in a 49° C. oven. The 30% IOA/NVP/PPG 725 solution was preparedby adding 700 grams of PPG 725 to 1000 grams of a 30% IOA/NVP copolymerin ethyl acetate/methanol to a 2 liter flask. The majority of thesolvent was distilled off at 125° C., and the residual solvent removedunder a vacuum of 2 mm Hg.

A resin was prepared by mixing 92 grams of part F from example 19 with40 grams of part I polyol solution from above and 28 grams of part Hpolyol solution from above for three minutes in a 500 ml beaker. 149grams of this resin material was mixed in a Hobart mixer with 300 gramsof H50/10,000 EPX glass bubbles forming a homogeneous composite. Thecomposite (V_(f) /V_(r) =4.2) was then calendered to 0.23 cm thicknessby repeatedly passing it through a rubber coated nip roller giving asheet about 8.25 cm by 1.8 m. The sheet was dusted with Talcum powder,rerolled, and stored in a moisture-proof pouch until use. For evaluationas a casting tape, the roll was immersed in a 23° C. water bath for 5seconds and rolled around a mandrel. The composite was sufficientlycreamy and cured to give a rigid cast.

Example 22 Casting Tape

A resin was prepared by mixing in a 1 liter beaker 170 grams of part F(from example 19) with 83 grams of part H (from example 21) and 22 gramsof a part "J" solution that was prepared according to the followingprocedure. In a one liter jar was added 60 grams of PPG 2025, 143 gramsof PPG 725, and 348 grams of a 30% solution of IOA/NVP copolymer in PPG725 (from example 21). The jar was shaken for 5 minutes, then 85.5 gramsof Arcol LHT 240 and 15.6 grams of MEMPE were added. The jar was shakenfor an additional 10 minutes, then placed in a 49° C. oven for 30minutes. The warmed components were then mixed with a high shear mixerfor 1 minute. 245 grams of the resulting homogeneous resin was pouredonto 300 grams of K-46 glass bubbles in a 4.5 liter metal mixing bowl.The contents were mixed using a Hobart mixer with a sigma blade forapproximately 3 minutes until the composite (V_(f) /V_(r) =2.8) becamehomogeneous.

A portion of the material was calendered to approximately 0.32 cm=2.8)thickness by repeated pressing between two rubber coated rollers. Thecomposite was taken down further to about 0.18 cm thickness by runningit through a pasta maker to give a sheet approximately 7 cm by 2.7 m.The sheet was then pressed between two layers of web (as described inExample 20) of like dimensions using the pasta maker to provide a tapeof 0.14 cm thickness. The sheet was rerolled without a core and sealedin a moisture proof pouch until use. For evaluation as a casting tape,the roll was removed from the pouch, immersed in a 23° C. water bath for15 seconds, then wound around a mandrel. The material was sufficientlycreamy to allow for molding the material, felt soft to the touch, andcured to give a rigid cast in 10 minutes.

Example 23 Alternative Application of Composite to Scrims

A small portion of the composite of Example 22 was put through the"spaghetti" making portion of the pasta maker to give long cords of thecomposite about 0.635 cm wide and 0.25 cm thick. The cords of compositewere longitudinally laid on top of the web of Example 20 (8.25 cm by 1m) using 6 cords across the width of the scrim. Another sample of web oflike dimension was placed on top of the composite and the material waspressed together by rolling the material with a metal knurled roller(7.6 cm diameter by 18 cm long with ridges running the length of theroll about 0.1 cm deep, 0.2 cm wide and 0.85 cm apart). The cords ofcomposite sandwiched between two layers of scrim were then pressedthrough the pasta maker to provide a 0.18 cm thick tape. The tape wasrerolled and stored in a moisture proof pouch until use. For evaluationas a casting tape, the sample was removed from the pouch, immersed in a23° C. water bath for 5 seconds, and rolled around a mandrel. Waterpenetration into and throughout the roll was excellent. In addition, thematerial was creamy and was easily molded to give a rigid cast in 10minutes.

Example 24 A Moldable Casting Tape

Preparation of Premix A-24: To a 1 liter jar under a nitrogen atmospherewas added 984 grams of Isonate 2143L, 2 grams of benzoyl chloride, 3grams of DB-100, and 7.6 grams of butylated hydroxytoluene. The contentswere mixed in a mechanical shaker for 10 minutes and stored at roomtemperature in a sealed jar.

Preparation of Premix B-24: To a 1 liter glass jar under a nitrogenatmosphere was added 365 grams Carbowax 600, 174 grams of LHT-240, 48grams of Pluronic F-108, 12 grams of MEMPE, and 17 grams of a 45% byweight solution of an IOA/NVP (75/25) copolymer in PPG 725. The jar wasplaced in a oven at 65.6° C. for 16 hours and placed in a mechanicalshaker for 10 minutes until it became homogeneous. The premix B wasstored at 65.6° C. until ready for use.

Preparation of the Composite and Article: The following was done in adry room kept at less than 5% humidity. To a 250 mL tripour beaker wasadded 112 grams of Premix A-24 and 78 grams of Premix B-24 and themixture stirred by hand with a wooden tongue depressor for 3 seconds.Next, 170 grams of this partially reacted resin was added to a 454 mljar containing 30 grams of Sil 35/34 filler. The contents were mixeduntil homogeneous by first shaking by hand and then stirring with arubber spatula.

A 7.6 cm×2.7 m piece of cheesecloth scrim (9.1×7.9 openings per cm) wasfed between a knife and bed of a steel knife coater with the knife setto provide a gap of 0.031 cm. The composite was quickly poured onto asmall portion of the scrim behind the knife and the scrim was coaledwith composite by pulling it through the gap at a rate of approximately15.24 cm/sec. The surface of the coated scrim was then lightly dustedwith K46 glass bubbles by feeding the scrim around a horizontal rollerthat was immersed in a reservoir containing K-46 glass bubbles. Thearticle was then rolled around a porous plastic core, stored in analuminum foil pouch, and the pouch placed in a oven at 65.6° C. for 2hours.

Preparation of a Cast: After the pouch had cooled to room temperature,the article was removed, dipped in a 23° C. water bath at for 5 seconds,and wound around a 5.1 cm diameter mandrel. The article was extremelymoldable and cured to provide a very smooth, rigid cast in less than 30minutes.

Example 25 Effect Of Filler Loading On Resin "Pooling"

To a 250 mL tripour beaker was added 124 grams of Premix A-24 (preparedas described above) and 76 grams of Premix B-24 (prepared as describedabove) and the mixture stirred with a tongue depressor for 3 seconds.Next, a portion of this resin was poured into a 454 ml glass jar thatcontained the Sil 35/34 filler. The jar was shaken by hand for 1 minutethen coated on three 7.6 cm×2.7 m pieces of cheesecloth scrim asdescribed above in Example 24. The following samples were prepared:

                  TABLE 25a                                                       ______________________________________                                        Run      Resin  Filler     Ave. Coating                                       No.      (gm)   (gm)       Wt. (g/m.sup.2)                                                                       V.sub.f /V.sub.r.sup.1                     ______________________________________                                        1        200    0          278     0.00                                       2        190    10         224.2   0.22                                       3        180    20         219.3   0.46                                       4        170    30         224.2   0.73                                       5        160    40         219.3   1.04                                       ______________________________________                                    

One drop of Reactint Red X52 (Millken Chemical Co., Spartanburg, S.C.)was placed near one edge of the coated scrim and the article was rolleraround a porous plastic core. The rolls were sealed in foil pouches andallowed to sit so that the width axis of the roll was in the verticalposition and the red dye was positioned at the top of the roll. Thesamples were allowed to sit at room temperature for 24 hours. Poolingwas determined on a scale of 0-5 with 0 representing no pooling and 5representing very high pooling of the coated material from the backing.In addition, the distance traveled by the dye down the vertical edge ofthe roll was used to quantify pooling of the material as was the amountof material left in the pouch upon removal of the roll after one day.

                  TABLE 25b                                                       ______________________________________                                        Run     Pooling   Distance Travelled                                                                         % Composite.sup.1 Left                         Number  Rating 1-5                                                                              By Dye (cm)  in Pouch                                       ______________________________________                                        1       5         7.6          27.77                                          2       3         6.4          5.92                                           3       1         0            2.66                                           4       0.5       0            1.75                                           5       0         0            1.2                                            ______________________________________                                         .sup.1 "% Composite Left in Pouch" was calculated by dividing the weight      of the pooled resin by the weight of the coated composite originally          present on the tape.                                                     

The thickness of an individual layer of coated scrim was measured (usingan Ames #2 thickness gauge available from Ames Company, Waltham, Mass.)before curing the roll and compared to the thickness of the uncoatedscrim. By subtraction, the thickness of the composite coating wascalculated.

Two--6 layer rings of each sample along with a Plaster of Paris control(Cellona) were prepared by dipping the roll for 15 seconds in 23° C.water, rolling the tape around a 5.1 cm diameter mandrel fitted withsynthetic stockinet, and molding the ring for several seconds. The 6layer rings were allowed to sit for 24 hrs. prior to testing for ringstrength. The Plaster of Paris control had an average ring strength of32.9 N/cm.

                  TABLE 25c                                                       ______________________________________                                        Run     Tape         Composite  Average Ring                                  Number  Thickness (cm)                                                                             Thickness (cm)                                                                           Strength (N/cm)                               ______________________________________                                        1       0.03         0.002      30.5                                          2       0.036        0.008      34.4                                          3       0.041        0.013      34.3                                          4       0.046        0.018      47.4                                          5       0.053        0.025      46.2                                          ______________________________________                                    

The data illustrates that very strong casting tapes can be produced bycoating a heavily filled composite on a light-weight scrim. Runs 3 to 5exhibited the least amount of pooling, with Runs 4 and 5 beingpreferred. Notably, Runs 3 to 5 each had a significant amount of"available" composite and were easily molded during application.

Example 26 Composite Viscosities

Several composites having different amounts of filler loading were madeto test composite viscosity as a function of volume percent filler. Eachsample was made using the ingredients described in Table 26a. Theprocedure for making Premix A-24 and Premix B-24 is described in Example24.

                  TABLE 26a                                                       ______________________________________                                        Run     Premix A-24                                                                             Premix B-24  Sil-35/34                                      No.     (gm)      (gm)         (gm)   V.sub.f /V.sub.r                        ______________________________________                                        1       112       68           0      0                                       2       112       68           5.6    0.14                                    3       112       68           17.8   0.41                                    4       112       68           24.5   0.57                                    5       112       68           31.7   0.73                                    6       112       68           45     1.04                                    7       56        34           30     1.39                                    ______________________________________                                    

Working in a low humidity, constant temperature room, the Sil-35/34filler was added to a 454 ml glass jar. To this, the respective amountsof Premix A-24 and Premix B-24 were sequentially added. The jar wascapped and shaken vigorously for 15 seconds and then stirred with arubber spatula for about five seconds until a homogenous mixture wasobtained. The jar was placed in a 45.6° C. oven for one hour and thenallowed to cool to room temperature. The viscosity was measured 7 daysafter the composite was made. Prior to testing the viscosity of eachcomposite, the composite was heated to 65.5° C. overnight and the samplewas stirred vigorously to ensure a homogenous solution of filler andresin. The sample was again allowed to cool to room temperature beforetesting.

Viscosity was measured using a Rheometrics Dynamic Analyzer II (RDA II)using a parallel plate geometry. All samples were tested under a drynitrogen environment at 25° C. using dynamic shear mode. Shear rate wasvaried from 0.1 to 100 rad/s. A strain amplitude of between 2 and 5% wasused. Viscosity as a function of filler concentration (at a fixed shearrate) is listed in Table 26b. For the sake of comparison, the Brookfieldviscosity of these samples was also measured (see Table 26c). Notably,Runs 6 and 7 had viscosities exceeding the capacity of this apparatus(i.e., greater than 2 million cP).

                  TABLE 26b                                                       ______________________________________                                              Viscosity (Pa                                                                           Viscosity Viscosity (Pa s                                                                        Viscosity (Pa s                            Run   s @       (Pa s @   @        @                                          No.   0.1 rad/s)                                                                              1 rad/s)  10 rad/s)                                                                              100 rad/s)                                 ______________________________________                                        1     28        28        35       34                                         2     68        68        56       48                                         3     190       175       134      112                                        4     366       225       177      163                                        5     600       367       336      264                                        6     4000      1430      782      600                                        7     36000     6o00      1094     1026                                       ______________________________________                                    

                  TABLE 26c                                                       ______________________________________                                        Run     Brookefield Viscosity                                                 No.     Spindle No.    RPM    Viscosity (cP)                                  ______________________________________                                        1       6              10     52,500                                          2       6              10     77,000                                          3       7              10     192,000                                         4       7              5      378,000                                         5       7              5      688,000                                         6       7              5      >2,000,000                                      7       --             --     --                                              ______________________________________                                    

Example 27 Surface Smoothness of a Casting Tape

The surface smoothness of a casting tape was measured after the productwas molded to show that the composite in this invention can bemanipulated such that the casting tape can be taken from a relativelyrough surface texture to a smooth surface texture by moving the resinaround during the molding of the cast.

A roll of a highly-filled composite coated casting tape was made byadding 30 Grams of Sil-35/34 low density filler; 112 grams of PremixA-24; and 68 Grams of Premix B-24 (heated to 65.5° C.) in order to a 454ml glass jar. The mixture was shaken vigorously by hand for severalseconds and then stirred for several seconds with a rubber spatula. Theresin was coated on a cheese cloth scrim as described in Example 24.After coating the cheese cloth scrim with composite the tape was rolledaround a 1.905 cm O.D×7.62 cm wide polyethylene core and packaged in analuminum foil laminate pouch.

Test samples were made using the above casting tape and, for comparison,a plaster of Paris casting tape. Surface smoothness of the products wasevaluated, as herein described, after the samples were molded. Flatslabs of each roll were prepared by fan-folding two layers of eachsample 25.4 cm long. Each sample was dipped in 24° C. water and spreadflat on a polyethylene lined counter top. The sample was smoothed byrubbing the tester's finger tips in a circular pattern with very lightpressure along the length of the slab until the product was cured to arelatively rigid state. Samples were allowed to sit at ambientconditions before testing for 14 hours.

The cured samples were tested using a Cyberscan laser measuring systemmanufactured by CyberOptics Corporation, 2505 Kennedy Street NE,Minneapolis, Minn., 55413. Test specimens were attached to a polyesterfilm backing using masking tape to hold the specimens flat duringtesting. The samples were scanned for surface smoothness over a 5.08 cmusing a 0.00254 cm step size and a sensor resolution of PRS 400.

The value reported in Table 27a is the Root Mean Square Value of theaverage height of the peaks and valleys detected by the laser detector.The RMS value was calculated by breaking the scan into thirds andaveraging the RMS of each section of the scan.

                  TABLE 27a                                                       ______________________________________                                        Sample ID           Average RMS (cm)                                          ______________________________________                                        Plaster of Paris    0.004                                                     Highly-filled composite Casting Tape                                                              0.007                                                     ______________________________________                                    

As can be seen in the above table, the surface smoothness of the castingtape of the present invention compares very favorably to plaster ofParis. In contrast, a traditional synthetic/fiberglass casting materialis very rough. In addition, the smooth casting tape of the presentinvention can be "autographed" (i.e., written on) just like a plaster ofParis cast.

Example 28

Preparation of Premix A-28: To a 3.8 liter jar under a nitrogenatmosphere was added 2201.6 grams of Isonate 2143L and 2.8 grams ofbenzoyl chloride. The contents were mixed by shaking and stored at roomtemperature in a sealed jar.

Preparation of Premix B-28: To a 3.8 liter jar under a nitrogenatmosphere was added 1700 grams Arcol PPG-725 (ARCO Chemical Co.,Newtown Square, Pa.), 7.2 grams DB antifoam (Dow Corning Corp., Midland,Mich.), 19.2 grams BHT, and 46.7 grams MEMPE. The contents were mixed byshaking and stored at room temperature in a sealed jar.

The following weighing, mixing and coating steps were done in a dry room(<3% RH). In a 237 ml jar was weighed 10 grams ofpoly(N-vinyl)pyrrolidone (average M_(w) ˜360,000, Aldrich Chemical Co.,Milwaukee, Wis.). This material had been previously treated by siftingit through a sieve (no. 30, 600 micron openings) and drying it in avacuum oven (at 90° C. and about 72.7 cm Hg vacuum) for 16 hours. 80.3 gPremix B-28 and 99.7 g Premix A-28 were weighed into the jar and mixedby shaking vigorously.

170 grams of the resulting resin containing dispersedpoly(N-vinyl)pyrrolidone was weighed into a one liter jar containing56.7 grams of Sil-35/34 (Sil-Cell brand, Silbrico Corp., Hodgkins, Ill.)which had been dried in a vacuum oven at 120° C. The jar was capped andthe contents mixed vigorously by shaking and then by further mixing witha spatula.

The resulting mixture was knife coated onto 28×24 bleached cotton gauzescrim (grade 50 cheesecloth from Twin City Janitor Supply, St. Paul,Minn.) and dried as above. The scrim (7.62 cm by 2.9 m) was placed onthe knife coater bed and the knife (bull nose type) was positioned overthe scrim at a distance of 0.0254 mm above the bed surface. A portion ofthe above mixture was poured in front of the knife on top of the scrimand the full length of the scrim was pulled by hand at a slow steadyrate under the knife. A total of three pieces of scrim were coated thisway with a mean coating weight of 7.6 grams composite mixture per gramof scrim. Each length was loosely rolled onto a perforated, 1.9 cmdiameter plastic core, sealed in a foil pouch, and stored for 24 hoursat 25° C.

The casting tape was removed from the pouch, dipped in 23° C. water for10 seconds with squeezing, and wrapped onto a stockinet covered,flexible plastic hand and arm. The material was very easily molded andsmoothed out so that overlapping areas could no longer be seen. Whencured, the surface of the cast was very smooth. The casting material setin about 3.5 minutes and formed a fully functional (weight-bearing) castin less than 60 minutes.

Example 29 Surface Smoothness Before and After Molding

Several samples of casting tape were tested to show the difference insurface smoothness after molding the samples. The following samples wereevaluated: 7.62 cm wide casting tape as described in Example 24 (Run 1),10.16 cm wide Carapace XF setting plaster of Paris (Carapace, Inc.Tulsa, Okla.), 7.62 cm wide Scotchcast™ Plus (3M Company, St. Paul,Minn.), and 7.62 cm wide resin impregnated cheesecloth prepared by firstmixing 199.4 grams part A-28 and 160.6 grams part B-28 in a 454 ml jarheating at 65.5° C. for 2 hours, cooling 21° C., and coating thecheesecloth as described in Example 28, giving a coating weight of 66.9grams resin on 7.2 grams cheesecloth (Comparison Run 2).

Each test sample was prepared by fan-folding two layers of the tape(each 25.4 cm long) and submerging in water for 15 seconds. Each samplewas placed flat on a polyethylene-lined lab bench top and smoothed byrotating the fingers in a circular direction while applying moderatepressure until the sample was cured.

A piece of cardboard 91.44 cm×91.44 cm was cut with a scissors so that a30.48 cm×15.25 cm rectangular opening was in the center of one edge ofthe sheet of cardboard. The cardboard was positioned vertically on adesk top such that the side of the cardboard with the opening was on thedesk. The sample of each molded casting tape described above was placedon one side of the opening in the cardboard. Several evaluators sat onthe opposite side of the cardboard from the samples, reached their armsthrough the opening in the cardboard and rubbed their finger tips on thecured molded sample. The evaluators were asked to compare the surfacesmoothness of the samples with a score of 1 being smoothest and a scoreof 4 being roughest. The results are listed in Table 29a.

                  TABLE 29a                                                       ______________________________________                                        Evaluator Plaster           Scotchcast ™                                   Number    Paris   Run 1     Plus     Run 2                                    ______________________________________                                        1         2       1         3        4                                        2         2       1         3        4                                        3         3       1         2        4                                        4         2       1         3        4                                        5         2       1         3        4                                        6         2       1         3        4                                        7         3       1         2        4                                        8         2       1         3        4                                        9         2       1         3        4                                        10        2       1         3        4                                        ______________________________________                                    

As can be seen from the above date, the evaluators rated the castingtape of Run 1 as having the smoothest surface.

Example 30 Viscosity of Water Activated Urethane Mixtures on CheeseclothScrim

From another roll of the material prepared in Example 28 were taken two20.3 cm lengths of coated gauze. Each was loosely folded into fourlayers and protected from moisture until the viscosity after wateractivation was measured. Viscosity was measured by dipping a four-layersection in 23° C. water for 10 seconds, gently rubbing the surface witha finger to ensure a smooth spread of the resin or composite on thecotton gauze, punching a 2.54 cm diameter section out, and placing thisbetween the two parallel plates of a Rheometrics Dynamic Analyzer II(RDA II) equipped with a 25 mm diameter parallel plate fixture withserrated plates. A compressive force of about 10 grams was used toensure a good contact with the sample. Steady shear viscositymeasurements at a shear rate of 0.2 s⁻¹ were made at 25° C. The firstdata point used as the initial viscosity of the material was collected70 seconds after the start of the water dip. This sample had an averageviscosity of 1.77×10⁴ Pa s.

A material similar to the material of Example 28 was prepared, buthaving 30 g Sil-35/34 mixed with 170 g mixture of Premix A-28 and B-28and being surface coated with K-46 glass bubbles as described in Example24. When tested as above a viscosity of 2.3×10⁴ Pa s was found. Whenevaluated as in Example 28, the material could be molded but could notbe smoothed out as easily as the Example 28 material.

A material prepared as described in Example 24 was tested as above. Twosamples gave a mean viscosity of 1.10×10⁴ Pa s.

A material similar to the material of Example 28 was prepared, but nopolyvinylpyrrolidone was used. When tested as above a viscosity of1.35×10⁴ Pa s was found. When evaluated as in Example 28 the materialcould not be molded by rubbing, and it stuck to the gloves of theapplier.

Example 31 Amount of Composite Material Available for Molding andSmoothing

Approximately 30 cm was removed from a roll of material prepared asdescribed in Example 24 and allowed to cure on a flat table top at 21°C. and 50% relative humidity for four hours. The thickness was found tobe about 1.1 mm using an Ames 202 micrometer (Ames, Waltham, Mass.).Using a razor blade, a section approximately 1 cm×3 cm was cut from thesample in the width direction. This was mounted with the cut edge up andexamined in a scanning electron microscope at 100×. The cotton yarncross sections (about 180 microns in diameter) were found to besurrounded by approximately 150 to 300 microns of composite material.Thus, a large amount of composite material was available for molding andsmoothing the material.

Example 32 Use of Amoco RFX Spunbonded Nonwoven as the Scrim

A 10.16 cm wide by 3 m long strip of 10 g/m² RFX spunbonded nonwovenfabric (AMOCO Fabrics and Fibers Company, Atlanta, Ga.) was coated asdescribed in Example 24, but at a pull rate of about 2.54 cm/sec. Afterstorage in a foil pouch at room temperature for 10 days, the roll wasrerolled very loosely onto another porous plastic core and sealed in afoil pouch in a room kept at less than 3% relative humidity. After 24hours, the coated RFX casting tape was evaluated as described in Example28. The material conformed well to the plastic hand and arm duringwrapping and was very easy to hand mold and smooth out; so that anyoverlap areas could no longer be seen, the surface was smooth, and theresulting cast followed the shape of the hand and arm. The material setin about 3 minutes and was a rigid east in 30 minutes.

What is claimed is:
 1. A method of making a light-weight orthopediccasting tape, comprising the steps of:mixing a polyisocyanate compound,a reactive hydrogen compound, and a filler to form a composite mixture;coating said composite mixture on a light-weight scrim while thepolyisocyanate compound and the reactive hydrogen compound are at mostonly partially reacted and while the composite mixture's viscosity islow enough so that the composite mixture can spread out on the scrim;and then allowing said polyisocyanate compound and said reactivehydrogen compound to further react, thereby forming a water-curableisocyanate-functional prepolymer and thereby increasing the viscosity ofsaid composite mixture to an extent that the composite mixture resistspooling during storage, wherein the ratio of the volume of said fillerdivided by the volume of said water-curable isocyanate-functionalprepolymer is greater than 0.4.
 2. The method according to claim 1,further comprising the step of:dusting additional amounts of said filleronto the surfaces of said coated scrim.
 3. A method of making alight-weight orthopedic casting tape, comprising the steps of:mixing apolyisocyanate compound, a reactive hydrogen compound, and a filler toform a composite mixture; coating said composite mixture on alight-weight scrim while the polyisocyanate compound and the reactivehydrogen compound are at most only partially reacted and while thecomposite mixture's viscosity is low enough so that the compositemixture can spread out on the scrim; and then allowing saidpolyisocyanate compound and said reactive hydrogen compound to furtherreact, thereby forming a water-curable isocyanate-functional prepolymerand thereby increasing the viscosity of said composite mixture to anextent that the composite mixture resists pooling during storage,wherein the ratio of the volume of said filler divided by the volume ofsaid water-curable isocyanate-functional prepolymer is greater than 0.8,and wherein said scrim has a basis weight less than 26 g/m² and isselected from the group consisting of cotton and polymeric knit, wovensand non-wovens.
 4. The method of claim 1, wherein said filler isselected from the group consisting of glass and ceramic bubbles havingan average particle diameter between 5 and 500 μm, and a specificgravity less than about 2, wherein the thickness of said casting tape isat least 100 microns greater than the thickness of said uncoated scrim,and wherein said composite mixture has a viscosity of at least 100 Pa swhen measured at 1 rad/s.
 5. The method of claim 4, wherein said castingtape, when cured, provides an exterior surface which is as smooth as aplaster of Paris cast.
 6. The method according to claim 1, wherein saidcoating step comprises the steps of: pouring said composite onto saidscrim and then pulling said scrim through the gap of a knife coater. 7.The method according to claim 6, wherein said coated scrim is thenprocessed by feeding said scrim past a horizontal roller that isimmersed in a reservoir containing additional filler.
 8. The methodaccording to claim 7, further comprising the step of:dusting additionalamounts of said filler onto the surfaces of said coated scrim.
 9. Themethod according to claim 1, wherein said mixing step is performed in adry environment having less than 5% relative humidity.
 10. A method ofmaking a light-weight orthopedic casting tape, comprising the stepsof:mixing a polyisocyanate compound, a reactive hydrogen compound, avolatile solvent and a filler to form a composite mixture; coating saidcomposite mixture on a light-weight scrim while the composite mixture'sviscosity is low enough so that the composite mixture can spread out onthe scrim; and then removing said volatile solvent, thereby increasingthe viscosity of said composite mixture to an extent that the compositemixture resists pooling during storage.
 11. The method according toclaim 10, further comprising the step of:dusting additional amounts ofsaid filler onto the surfaces of said coated scrim.
 12. The method ofclaim 10, wherein the polyisocyanate compound and reactive hydrogencompound form a water-curable isocyanate-functional prepolymer and theratio of the volume of said filler divided by the volume of saidwater-curable isocyanate-functional prepolymer is greater than 0.8, andwherein said scrim has a basis weight less than 26 g/m² and is selectedfrom the group consisting of cotton and polymeric knit, wovens andnon-wovens.
 13. The method of claim 10, wherein said filler is selectedfrom the group consisting of glass and ceramic bubbles having an averageparticle diameter between 5 and 500 μm, and a specific gravity less thanabout 2, wherein the thickness of said casting tape is at least 100microns greater than the thickness of said uncoated scrim, and whereinsaid composite mixture has a viscosity of at least 100 Pa s whenmeasured at 1 rad/s.
 14. The method of claim 1, wherein the ratio of thevolume of said filler divided by the volume of said water-curableisocyanate-functional prepolymer is greater than 0.8.
 15. The method ofclaim 1, wherein the filler is present in the composite in an amountbetween 30 and 85 percent by volume.
 16. The method of claim 1, whereinthe filler is present in the composite in an amount between 40 and 75percent by volume.
 17. The method of claim 1, wherein said water-curableisocyanate-functional prepolymer has an NCO/OH ratio greater than 3.0.